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  • 1.
    Al-Furoukh, Natalie
    et al.
    Max-Planck-Institute for Heart and Lung Research, Ludwigstrasse 43, 61231 Bad Nauheim, Germany.
    Goffart, Steffi
    Szibor, Marten
    Wanrooij, Sjoerd
    Braun, Thomas
    Binding to G-quadruplex RNA activates the mitochondrial GTPase NOA1.2013In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1833, no 12Article in journal (Refereed)
    Abstract [en]

    NOA1 is an evolutionary conserved, nuclear encoded GTPase essential for mitochondrial function and cellular survival. The function of NOA1 for assembly of mitochondrial ribosomes and regulation of OXPHOS activity depends on its GTPase activity, but so far no ligands have been identified that regulate the GTPase activity of NOA1. To identify nucleic acids that bind to the RNA-binding domain of NOA1 we employed SELEX (Systemic Evolution of Ligands by EXponential Enrichment) using recombinant mouse wildtype NOA1 and the GTPase mutant NOA1-K353R. We found that NOA1 binds specifically to oligonucleotides that fold into guanine tetrads (G-quadruplexes). Binding of G-quadruplex oligonucleotides stimulated the GTPase activity of NOA1 suggesting a regulatory link between G-quadruplex containing RNAs, NOA1 function and assembly of mitochondrial ribosomes.

  • 2. Bernbäck, S
    et al.
    Bläckberg, Lars
    Hernell, Olle
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Paediatrics.
    Fatty acids generated by gastric lipase promote human milk triacylglycerol digestion by pancreatic colipase-dependent lipase.1989In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1001, no 3, p. 286-93Article in journal (Refereed)
    Abstract [en]

    The concerted action of purified bovine gastric lipase and human pancreatic colipase-dependent lipase and colipase, or crude human pancreatic juice, in the digestion of human milk triacylglycerols was explored in vitro. Gastric lipase hydrolyzed milk triacylglycerol with an initially high rate but became severely inhibited already at low concentration of released fatty acid. In contrast, colipase-dependent lipase could not, by itself, hydrolyze milk triacylglycerol. However, a short preincubation of milk with gastric lipase, resulting in a limited lipolysis, made the milk fat triacylglycerol available for an immediate and rapid hydrolysis by pancreatic juice, and also for purified colipase-dependent lipase, provided colipase and bile salts were present. The same effect was obtained when incubation with gastric lipase was replaced by addition of long-chain fatty acid. Long-chain fatty acid increased the binding of colipase-dependent lipase to the milk fat globule. Binding was efficient only in the presence of both fatty acid and colipase. We conclude that a limited gastric lipolysis of human milk triacylglycerol, resulting in a release of a low concentration of long-chain fatty acids, is of major importance for the subsequent hydrolysis by colipase-dependent lipase in the duodenum.

  • 3. Bernbäck, S
    et al.
    Hernell, Olle
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Paediatrics.
    Bläckberg, Lars
    Bovine pregastric lipase: a model for the human enzyme with respect to properties relevant to its site of action.1987In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 922, no 2, p. 206-13Article in journal (Refereed)
    Abstract [en]

    Preduodenal lipolysis is considered to promote efficient lipid digestion in the neonatal period. The lipase(s) responsible may be of pregastric or gastric origin depending upon the species. We have previously reported on purification and molecular characterization of a pregastric lipase from calf. Antibodies to this bovine enzyme crossreact with a protein of similar size in human gastric contents and also inhibit its lipolytic activity. Since the bovine and human enzymes also have similar kinetic properties, the view is favoured that the bovine enzyme can be used as a model for physiological studies relevant to human neonates. In contrast to the lipases operating in the small intestine pregastric lipase has the unique property of initiating the hydrolysis of human milk fat globule triacylglycerol. In order to do this no cofactor is required. Pregastric lipase was stable at low pH and had an acid-pH optimum. Furthermore, it was extremely resistant to pepsin. In contrast, pancreatic proteinases, i.e. trypsin and chymotrypsin, inactivated the enzyme. The rate of inactivation was increased in the presence of bile salts which by themselves could inhibit enzyme activity. Thus, pregastric lipase is ideally suited for activity in the stomach but will not, under healthy conditions, contribute to lipid digestion in the duodenum.

  • 4. Bhalerao, RP
    et al.
    Gillbro, T
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Structure and energy-transfer of the phycobilisome in a linker protein replacement mutant of cyanobacterium synechococcus-79421991In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1060, no 1, p. 59-66Article in journal (Refereed)
    Abstract [en]

    The role of the linker proteins in the biogenesis and energy transfer of the phycobilisome rod was monitored by making insertional inactivation in the cpcI gene coding for the core-proximal 33 kilodalton (kDa) protein in the cyanobacterium Synechococcus 7942. The insertion leaves the cpcH gene coding for the core-distal 30 kDa protein intact and functional. Analysis of the phycobilisome protein composition of the cpcI mutant shows that the 30 kDa protein is present in normal amounts in the rod, indicating that the 30 kDa linker protein can replace the 33 kDa protein in the biogenesis and structural integrity of the rod. The absorption and fluorescence characteristics of the mutated phycobilisome is almost indistinguishable from that of the wild-type of the same rod length. The fluorescence kinetics from the cpcI mutant show that the dominating decay component has a lifetime from phycocyanin of 69 ps as compared to 72 ps found for the wild-type phycobilisome with the same rod length. The results show that replacing the 33 kDa for the 30 kDa linker in the rod does not alter the energy harvesting or the energy transfer characteristics of the rod in contrast to what has been concluded from data obtained from in vitro experiments. We conclude that the linker polypeptides have only a minor influence on the energy transfer characteristics of the rod but are mainly involved in determining the length of the rod in response to changing environmental light conditions.

  • 5. Björquist, P
    et al.
    Brohlin, Maria
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Biomedical Laboratory Science.
    Ehnebom, J
    Ericsson, M
    Kristiansen, C
    Pohl, G
    Deinum, J
    Plasminogen activator inhibitor type-1 interacts exclusively with the proteinase domain of tissue plasminogen activator.1994In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1209, no 2, p. 191-202Article in journal (Refereed)
    Abstract [en]

    Two different techniques have been used to study the complex formation of recombinant human plasminogen activator inhibitor type-1, PAI-1, with either recombinant human two-chain tissue plasminogen activator, tc tPA (EC 3.4.21.68), or the tPA deletion variants tc K2P, containing the kringle 2 domain and the proteinase domain, and P, containing only the proteinase domain. The same value for Kon, 2.10(7) M-1s-1 for binding of PAI-1 was found for the three tPA forms by direct detection of the complex formation in real time by surface plasmon resonance, BIAcore, or indirectly by monitoring the time course of the inhibition of tPA using the chromogenic substrate N-methylsulfonyl-D-Phe-Gly-Arg-4-pNA-acetate. Apparently, no conformational change is involved in the rate-limiting step, since the kon value was found to be independent of the temperature from 20 to 35 degrees C. By the BIAcore technique, it was found that the complex between PAI-1 and tPA covalently coupled to the surface, was stable at 25 degrees C, since no dissociation was seen in buffer. However, extended treatment with 1 M NH4OH destroyed the complex with t 1/2 = 5 h. The same kon values and complex composition were found by measuring either the binding of tPA to PAI-1 captured on the monoclonal antibody MAI-11 or the binding of PAI-1 to tPA captured on the monoclonal antibody 2:2 B10. Quantification of the complex composition between PAI-1 captured on the monoclonal antibody MAI-11 with either tPA, K2P or P gave a one-to-one ratio with the fraction of active PAI-1, consistent with the results from SDS-PAGE and the specific activity of PAI-1. The complexes of the three tPA forms with PAI-1 captured on a large surface of MAI-11 dissociated more rapidly from MAI-11, with the same apparent koff, kdis, = 2.10(-3) s-1, compared with 0.7-10(-3) s-1 for the dissociation of PAI-1 alone. In consistance, the Kd, calculated from the direct determination of the kon and koff for the association of different form of PAI-1 to a small surface of MAI-11, was found to be higher for PAI-1 in complex with tPA than for free active PAI-1. Apparently, upon complex formation, a change is induced in PAI-1 at the binding epitope for MAI-11.(ABSTRACT TRUNCATED AT 400 WORDS)

  • 6. BRENTEL, I
    et al.
    Selstam, Eva
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    LINDBLOM, G
    PHASE-EQUILIBRIA OF MIXTURES OF PLANT GALACTOLIPIDS - THE FORMATION OF A BICONTINUOUS CUBIC PHASE1985In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 812, no 3, p. 816-826Article in journal (Refereed)
  • 7. Christiansen, Maja
    et al.
    Jørgensen, Charlotte S
    Laursen, Inga
    Hirschberg, Daniel
    Højrup, Peter
    Houen, Gunnar
    Protein chemical characterization of Gc globulin (vitamin D-binding protein) isoforms; Gc-1f, Gc-1s and Gc-2.2007In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1774, no 4Article in journal (Refereed)
    Abstract [en]

    Gc globulin, also called vitamin D-binding protein, is a plasma protein involved in the extracellular actin-scavenger system, vitamin D transport and possibly also other biological activities. Low levels of Gc globulin have been found to correlate with multiple organ failure and non-survival of patients with fulminant hepatic failure and trauma. Here, we characterize the dominant isoforms of plasma-derived Gc globulin from Cohn fraction IV paste with respect to amino acid sequence and posttranslational modifications. Gc globulin was purified in large scale and the isoforms separated by ion exchange chromatography. The separated isoforms and several commercial preparations of individual isoforms were characterized by mass spectrometry. This revealed that the major isoforms were non-glycosylated. Compared to the Gc-1f isoform the other dominating isoforms represented an Asp/Glu substitution (Gc-1s) and a Thr/Lys substitution (Gc-2) in agreement with DNA sequencing studies. The commercial preparations were found to represent mainly one or two isoforms. An O-linked glycan with a mass of 656 Da and terminating with a sialic acid residue was detected on a minor proportion of Gc globulin molecules.

  • 8.
    Conlan, Brendon
    et al.
    Australian National University, Canberra, Australia.
    Cox, Nicholas
    Australian National University, Canberra, Australia.
    Su, Ji-Hu
    Max Planck Institute for Bioinorganic Chemistry, Mülheim an der Ruhr, Germany.
    Hillier, Warwick
    Australian National University, Canberra, Australia.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lubitz, Wolfgang
    Max Planck Institute for Bioinorganic Chemistry, Mülheim an der Ruhr, Germany.
    Dutton, P Leslie
    University of Pennsylvania, Philadelphia, USA.
    Wydrzynski, Tom
    Australian National University, Canberra, Australia.
    Photo-catalytic oxidation of a di-nuclear manganese centre in an engineered bacterioferritin 'reaction centre'2009In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1787, no 9, p. 1112-1121Article in journal (Refereed)
    Abstract [en]

    Photosynthesis involves the conversion of light into chemical energy through a series of electron transfer reactions within membrane-bound pigment/protein complexes. The Photosystem II (PSII) complex in plants, algae and cyanobacteria catalyse the oxidation of water to molecular O(2). The complexity of PSII has thus far limited attempts to chemically replicate its function. Here we introduce a reverse engineering approach to build a simple, light-driven photo-catalyst based on the organization and function of the donor side of the PSII reaction centre. We have used bacterioferritin (BFR) (cytochrome b1) from Escherichia coli as the protein scaffold since it has several, inherently useful design features for engineering light-driven electron transport. Among these are: (i.) a di-iron binding site; (ii.) a potentially redox-active tyrosine residue; and (iii.) the ability to dimerise and form an inter-protein heme binding pocket within electron tunnelling distance of the di-iron binding site. Upon replacing the heme with the photoactive zinc-chlorin e(6) (ZnCe(6)) molecule and the di-iron binding site with two manganese ions, we show that the two Mn ions bind as a weakly coupled di-nuclear Mn(2)(II,II) centre, and that ZnCe(6) binds in stoichiometric amounts of 1:2 with respect to the dimeric form of BFR. Upon illumination the bound ZnCe(6) initiates electron transfer, followed by oxidation of the di-nuclear Mn centre possibly via one of the inherent tyrosine residues in the vicinity of the Mn cluster. The light dependent loss of the Mn(II) EPR signals and the formation of low field parallel mode Mn EPR signals are attributed to the formation of Mn(III) species. The formation of the Mn(III) is concomitant with consumption of oxygen. Our model is the first artificial reaction centre developed for the photo-catalytic oxidation of a di-metal site within a protein matrix which potentially mimics WOC photo-assembly.

  • 9.
    Elo, Mika
    et al.
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Kaarniranta, Kai
    Department of Opthalmology, Kuopio University Hospital, Kuopio, Finland.
    Helminen, Heikki
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Lammi, Mikko
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Hsp90 inhibitor geldanamycin increases hsp70 mRNA stabilisation but fails to activate HSF1 in cells exposed to hydrostatic pressure.2005In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1743, no 1-2, p. 115-119, article id 15777846Article in journal (Refereed)
    Abstract [en]

    High hydrostatic pressure (HP) increases Hsp70 protein and mRNA levels by increasing the mRNA half-life without activation of HSF1 transcription factor. We investigated whether this change in gene expression requires Hsp90, previously shown to regulate hsp70 genes via HSF1. In HeLa cells, both HP and Hsp90 inhibitor geldanamycin (GA) up-regulated Hsp70 expression through mRNA stabilisation. GA, unlike HP, increased HSF1 activation. However, when exposures were used together a marked Hsp70 response was observed with mRNA stabilisation without coincidence of HSF1 activation. Our data suggests that Hsp90 is involved in hsp70 mRNA stabilisation and the HSF1 activation can be suppressed by high HP.

  • 10.
    Frisan, Teresa
    Dept. Cell and Molecular Biology, Karolinska Institutet.
    Bacterial genotoxins: the long journey to the nucleus of mammalian cells2016In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1858, no 3, p. 567-575, article id S0005-2736(15)00267-9Article, review/survey (Refereed)
    Abstract [en]

    Bacterial protein genotoxins target the DNA of eukaryotic cells, causing DNA single and double strand breaks. The final outcome of the intoxication is induction of DNA damage responses and activation of DNA repair pathways. When the damage is beyond repair, the target cell either undergoes apoptosis or enters a permanent quiescent stage, known as cellular senescence. In certain instances, intoxicated cells can survive and proliferate. This event leads to accumulation of genomic instability and acquisition of malignant traits, underlining the carcinogenic potential of these toxins. The toxicity is dependent on the toxins' internalization and trafficking from the extracellular environment to the nucleus, and requires a complex interaction with several cellular membrane compartments: the plasma membrane, the endosomes, the trans Golgi network and the endoplasmic reticulum, and finally the nucleus. This review will discuss the current knowledge of the bacterial genotoxins internalization pathways and will highlight the issues that still remain unanswered. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.

  • 11.
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    METABOLITE LEVELS IN THE CHLOROPLAST AND EXTRACHLOROPLAST COMPARTMENTS OF BARLEY LEAF PROTOPLASTS DURING THE INITIAL PHASE OF PHOTOSYNTHETIC INDUCTION1993In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1183, no 2, p. 327-332Article in journal (Refereed)
    Abstract [en]

    Metabolite levels were determined in the chloroplast and extrachloroplast compartments of barley protoplasts during photosynthetic induction using rapid fractionation by membrane filtration. This method allowed studies with a high time resolution the first determination of subcellular metabolite content bring made after only 0.3 s. Upon illumination, dark-adapted protoplasts exhibited a 1 min lag phase prior to commencement of oxygen evolution, and the maximum rate was reached after 4 to 5 min. In contrast to oxygen evolution, the ATP/ADP ratio in the chloroplasts increased from 1 to 2 within 0.5 s and reached a maximum of about 5 after 2 s. There was a dramatic increase in the extrachloroplastic ATP/ADP ratio within a few seconds, reaching a maximum after about 15 s. During the initial phase of photosynthetic induction, the subcellular ATP/ADP ratios were very similar in photorespiratory (low CO,) and non-photorespiratory (high CO,) conditions. The ATP/ADP ratios in both the chloroplast and extrachloroplast compartments remained high until photosynthetic oxygen evolution started and then decreased when the photosynthetic rate reached its maximum. In steady-state photosynthesis the subcellular ATP/ADP ratios were considerably higher under photorespiratory conditions as compared to non-photorespiratory conditions. During the initial phase of photosynthetic induction, 3-phosphoglycerate decreased and triose phosphates increased both in the chloroplast and extrachloroplast compartments. The changes in these metabolites are consistent with a 3-phosphoglycerate/triose phosphate shuttle using the phosphate translocator as the means to supply ATP to the cytosol during photosynthetic induction.

  • 12.
    Havelius, Kajsa G V
    et al.
    Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
    Su, Ji-Hu
    Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China.
    Han, Guangye
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mamedov, Fikret
    Molecular Biomimetics, Department of Photochemistry and Molecular Science, Uppsala University, The Ångström Laboratory, P.O. Box 523, S-751 20 Uppsala, Sweden.
    Ho, Felix M
    Molecular Biomimetics, Department of Photochemistry and Molecular Science, Uppsala University, The Ångström Laboratory, P.O. Box 523, S-751 20 Uppsala, Sweden.
    Styring, Stenbjörn
    Molecular Biomimetics, Department of Photochemistry and Molecular Science, Uppsala University, The Ångström Laboratory, P.O. Box 523, S-751 20 Uppsala, Sweden.
    The formation of the split EPR signal from the S(3) state of Photosystem II does not involve primary charge separation2011In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1807, no 1, p. 11-21Article in journal (Refereed)
    Abstract [en]

    Metalloradical EPR signals have been found in intact Photosystem II at cryogenic temperatures. They reflect the light-driven formation of the tyrosine Z radical (Y(Z)) in magnetic interaction with the CaMn(4) cluster in a particular S state. These so-called split EPR signals, induced at cryogenic temperatures, provide means to study the otherwise transient Y(Z) and to probe the S states with EPR spectroscopy. In the S(0) and S(1) states, the respective split signals are induced by illumination of the sample in the visible light range only. In the S(3) state the split EPR signal is induced irrespective of illumination wavelength within the entire 415-900nm range (visible and near-IR region) [Su, J. H., Havelius, K. G. V., Ho, F. M., Han, G., Mamedov, F., and Styring, S. (2007) Biochemistry 46, 10703-10712]. An important question is whether a single mechanism can explain the induction of the Split S(3) signal across the entire wavelength range or whether wavelength-dependent mechanisms are required. In this paper we confirm that the Y(Z) radical formation in the S(1) state, reflected in the Split S(1) signal, is driven by P680-centered charge separation. The situation in the S(3) state is different. In Photosystem II centers with pre-reduced quinone A (Q(A)), where the P680-centered charge separation is blocked, the Split S(3) EPR signal could still be induced in the majority of the Photosystem II centers using both visible and NIR (830nm) light. This shows that P680-centered charge separation is not involved. The amount of oxidized electron donors and reduced electron acceptors (Q(A)(-)) was well correlated after visible light illumination at cryogenic temperatures in the S(1) state. This was not the case in the S(3) state, where the Split S(3) EPR signal was formed in the majority of the centers in a pathway other than P680-centered charge separation. Instead, we propose that one mechanism exists over the entire wavelength interval to drive the formation of the Split S(3) signal. The origin for this, probably involving excitation of one of the Mn ions in the CaMn(4) cluster in Photosystem II, is discussed.

  • 13.
    Hultin, M
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Physiological chemistry.
    Bengtsson-Olivecrona, G
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Physiological chemistry.
    Olivecrona, T
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Physiological chemistry.
    Release of lipoprotein lipase to plasma by triacylglycerol emulsions. Comparison to the effect of heparin.1992In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1125, no 1, p. 97-103Article in journal (Refereed)
    Abstract [en]

    It was previously known that lipoprotein lipase (LPL) activity in plasma rises after infusion of a fat emulsion. To explore the mechanism we have compared the release of LPL by emulsion to that by heparin. After bolus injections of a fat emulsion (Intralipid) to rats, plasma LPL activity gradually rose 5-fold to a maximum at 6-8 min. During the same time the concentration of injected triacylglycerols (TG) decreased by about half. Hence, the time-course for plasma LPL activity was quite different from that for plasma TG. The disappearance of injected 125I-labelled bovine LPL from circulation was retarded by emulsion. This effect was more marked 30 min than 3 min after injection of the emulsion. The data indicate that the release of LPL into plasma is not solely due to binding of the lipase to the emulsion particles as such, but involves metabolism of the particles. Emulsion increased the fraction of labelled LPL found in adipose tissue, heart and the red muscle studied, but had no significant effect on the fraction found in liver. The effects of emulsion were quite different from those of heparin, which caused an immediate release of the lipase to plasma, decreased uptake of LPL in most extrahepatic tissues by 60-95%, and increased the fraction taken up in the liver.

  • 14.
    Hörnberg, Andreas
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine).
    Eneqvist, Therese
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Lundgren, Erik
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    The β-strand D of transthyretin trapped in two discrete conformations2004In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1700, no 1, p. 93-104Article in journal (Refereed)
    Abstract [en]

    Conformational changes in native and variant forms of the human plasma protein transthyretin (TTR) induce several types of amyloid diseases. Biochemical and structural studies have mapped the initiation site of amyloid formation onto residues at the outer C and D beta-strands and their connecting loop. In this study, we characterise an engineered variant of transthyretin, Ala108Tyr/Leu110Glu, which is kinetically and thermodynamically more stable than wild-type transthyretin, and as a consequence less amyloidogenic. Crystal structures of the mutant were determined in two space groups, P2(1)2(1)2 and C2, from crystals grown in the same crystallisation set-up. The structures are identical with the exception for residues Leu55-Leu58, situated at beta-strand D and the following DE loop. In particular, residues Leu55-His56 display large shifts in the C2 structure. There the direct hydrogen bonding between beta-strands D and A has been disrupted and is absent, whereas the beta-strand D is present in the P2(1)2(1)2 structure. This difference shows that from a mixture of metastable TTR molecules, only the molecules with an intact beta-strand D are selected for crystal growth in space group P2(1)2(1)2. The packing of TTR molecules in the C2 crystal form and in the previously determined amyloid TTR (ATTR) Leu55Pro crystal structure is close-to-identical. This packing arrangement is therefore not unique in amyloidogenic mutants of TTR.

  • 15.
    Jansson, Stefan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Selstam, Eva
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    THE RAPIDLY PHOSPHORYLATED 25-KDA POLYPEPTIDE OF THE LIGHT-HARVESTING COMPLEX OF PHOTOSYSTEM-II IS ENCODED BY THE TYPE-2 CAB-II GENES1990In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1019, no 2, p. 110-114Article in journal (Refereed)
  • 16.
    Johansson, Marcus J O
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Xu, Fu
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Byström, Anders S
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Elongator-a tRNA modifying complex that promotes efficient translational decoding2018In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1861, no 4, p. 401-408Article in journal (Refereed)
    Abstract [en]

    Naturally occurring modifications of the nucleosides in the anticodon region of tRNAs influence their translational decoding properties. Uridines present at the wobble position in eukaryotic cytoplasmic tRNAs often contain a 5-carbamoylmethyl (ncm5) or 5-methoxycarbonylmethyl (mcm5) side-chain and sometimes also a 2-thio or 2'-O-methyl group. The first step in the formation of the ncm5 and mcm5 side-chains requires the conserved six-subunit Elongator complex. Although Elongator has been implicated in several different cellular processes, accumulating evidence suggests that its primary, and possibly only, cellular function is to promote modification of tRNAs. In this review, we discuss the biosynthesis and function of modified wobble uridines in eukaryotic cytoplasmic tRNAs, focusing on the in vivo role of Elongator-dependent modifications in Saccharomyces cerevisiae. 

  • 17. Mambule, C
    et al.
    Ando, Y
    Anan, Intissar
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Holmgren, G
    Sandgren, O
    Stigbrandt, T
    Tashima, K
    Suhr, Ole B
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Enhancement of AA-amyloid formation in mice by transthyretin amyloid fragments and polyethylene glycol.2000In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1474, no 3, p. 331-6Article in journal (Refereed)
    Abstract [en]

    The mechanism behind amyloid formation is unknown in all types of amyloidosis. Several substances can enhance amyloid formation in animal experiments. To induce secondary systemic amyloid (AA-type amyloid) formation, we injected silver nitrate into mice together with either amyloid fibrils obtained from patients with familial polyneuropathy (FAP) type I or polyethylene glycol (PEG). Mice injected with silver nitrate only served as controls. Amyloid deposits were detectable at day 3 in animals injected with amyloid fibrils and in those injected with PEG, whereas in control mice, deposits were not noted before day 12. Our results indicate that amyloid fibrils from FAP patients and even a non-sulfate containing polysaccharide (PEG) have the potential to act as amyloid-enhancing factors.

  • 18. Neirinckx, Virginie
    et al.
    Hedman, Håkan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Niclou, Simone P.
    Harnessing LRIG1-mediated inhibition of receptor tyrosine kinases for cancer therapy2017In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1868, no 1, p. 109-116Article, review/survey (Refereed)
    Abstract [en]

    Leucine-rich repeats and immunoglobulin-like domains containing protein 1 (LRIG1) is an endogenous feedback regulator of receptor tyrosine kinases (RTKs) and was recently shown to inhibit growth of different types of malignancies. Additionally, this multifaceted RTK inhibitor was reported to be a tumor suppressor, a stem cell regulator, and a modulator of different cellular phenotypes. This mini-review provides a concise and up-to-date summary about the known functions of LRIG1 and its related family members, with a special emphasis on underlying molecular mechanisms and the opportunities for harnessing its therapeutic potential against cancer. 

  • 19.
    Nordlund, I
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Shingler, V
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Nucleotide sequences of the meta-cleavage pathway enzymes 2-hydroxymuconic semialdehyde dehydrogenase and 2-hydroxymuconic semialdehyde hydrolase from Pseudomonas CF600.1990In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1049, no 2Article in journal (Refereed)
    Abstract [en]

    The nucleotide sequence of a 2493 base pair (bp) region, spanning the coding regions for the meta-cleavage pathway enzymes 2-hydroxymuconic semialdehyde dehydrogenase (HMSD) and 2-hydroxymuconic semialdehyde hydrolase (HMSH), was determined. The deduced protein sequence for HMSD is 486 amino acid residues long with an Mr of 51,682. HMSD has homology with a number of aldehyde dehydrogenases from various eukaryotic sources. The deduced protein sequence for HMSH is 283 amino acids long with an Mr of 30,965. The amino acid composition of this enzyme is similar to that of isofunctional enzymes from toluene and m-cresol catabolic pathways.

  • 20.
    Ny, Tor
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Thomale, J
    Hjalmarsson, K
    Nass, G
    Björk, G R
    Non-coordinate regulation of enzymes involved in transfer RNA metabolism in Escherichia coli.1980In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 607, no 2, p. 277-84Article in journal (Refereed)
    Abstract [en]

    During different steady state growth conditions in Escherichia coli the level of the three tRNA-modifying enzymes, the tRNA(m5Urd)-, tRNA(m1Guo)- and tRNA(mam5s2Urd)methyltransferase and of five aminoacyl-tRNA synthetases, the leucyl-, valyl-, isoleucyl-, arginyl- and threonyl-tRNA-synthetase, has been determined. It is shown that those two classes of tRNA affecting enzymes are not coordinately regulated and that even within these two groups of enzymes the constituents are regulated independently of each other. Furthermore it is demonstrated that none of the aminoacyl-tRNA synthetases and only one of the three tRNA-methyltransferases, the tRNA(m5Urd)methyltransferase, is under control of the relA+-gene.

  • 21.
    Orädd, Greger
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Schmidtchen, Artur
    Malmsten, Martin
    Effects of peptide hydrophobicity on its incorporation in phospholipid membranes - an NMR and ellipsometry study2011In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1808, no 1, p. 244-252Article in journal (Refereed)
    Abstract [en]

    Effects of peptide hydrophobicity on lipid membrane binding, incorporation, and defect formation was investigated for variants of the complement-derived antimicrobial peptide CNY21 (CNYITELRRQHARASHLGLAR), in anionic 1-palmitoyl-2-oleoylphosphatidylethanolamine (POPE)/1-palmitoyl-2-oleoylphosphatidylglycerol (POPG) and zwitterionic 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) membranes. Using a method combination of, e.g., ellipsometry, CD, and fluorescence spectroscopy, it was shown that peptide adsorption, as well as peptide-induced liposome leakage and bactericidal potency against Escherichia coli and Pseudomonas aeruginosa, was promoted by increasing the hydrophobicity of CNY21 through either substituting the two histidines (H) in CNY21 with more hydrophobic leucine (L) residues, or end-tagging with tritryptophan (WWW). Fluorescence spectroscopy revealed that both CNY21WWW and the WWW tripeptide localized to the polar headgroup region of these phospholipid membranes. Deuterium NMR experiments on macroscopically oriented membranes containing fully (palmitoyl) deuterated POPC (POPC-d(31)) demonstrated that both CNY21L and CNY21WWW induced disordering of the lipid membrane. In contrast, for cholesterol-supplemented POPC-d(31) bilayers, peptide-induced disordering was less pronounced in the case of CNY21L, indicating that the peptide is unable to partition to the interior of the lipid membrane in the presence of cholesterol. CNY21WWW, on the other hand, retained its membrane-disordering effect also for cholesterol-supplemented POPC-d(31). These findings were supported by pulsed field gradient NMR experiments where the lateral lipid diffusion was determined in the absence and presence of peptides. Overall, the results provide some mechanistic understanding to previously observed effects of peptide hydrophobization through point mutations and end-tagging, particularly so for complement-based antimicrobial peptides.

  • 22. PETIT, PX
    et al.
    EDMAN, KA
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    ERICSON, I
    SOME PROPERTIES OF MITOCHONDRIA, MITOPLASTS AND SUBMITOCHONDRIAL PARTICLES OF DIFFERENT POLARITIES FROM PLANT-TISSUES1987In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 890, no 3, p. 377-386Article in journal (Refereed)
  • 23.
    Pozdnyakova, Irina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wittung-Stafshede, Pernilla
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Non-linear effects of macromolecular crowding on enzymatic activity of multi-copper oxidase2010In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1804, no 4, p. 740-744Article in journal (Refereed)
    Abstract [en]

    Enzymes catalyze biochemical reactions in highly crowded environments where the amount of macromolecules may occupy up to 40% of the volume. Here we report how cell-like conditions tune catalytic parameters for the monomeric multi-copper oxidase, Saccharomyces cerevisiae Fet3p, in vitro. At low amounts of crowding agent, we detect increases in both of K(M) (weaker substrate binding) and k(cat) (improved catalytic efficiency), whereas at higher crowding levels, both parameters were reduced. Presence of crowding agents does not affect Fet3p structural content but increases thermal resistance. The observations are compatible with ordering of a non-optimal substrate-binding site and restricted internal dynamics as a result of excluded volume effects making the protein less structurally 'strained'.

  • 24.
    Qu, Cheng-Juan
    et al.
    Department of Anatomy, Institute of Biomedicine, University of Kuopio, Kuopio, Finland.
    Karjalainen, Hannu
    Department of Anatomy, Institute of Biomedicine, University of Kuopio, Kuopio, Finland.
    Helminen, Heikki
    Department of Anatomy, Institute of Biomedicine, University of Kuopio, Kuopio, Finland.
    Lammi, Mikko
    Department of Anatomy, Institute of Biomedicine, University of Kuopio, Kuopio, Finland.
    The lack of effect of glucosamine sulphate on aggrecan mRNA expression and (35)S-sulphate incorporation in bovine primary chondrocytes.2006In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1762, no 4, p. 453-459, article id 16504489Article in journal (Refereed)
    Abstract [en]

    Glucosamine and glucosamine sulphate have been promoted as a disease-modifying agent to improve the clinical symptoms of osteoarthritis. The precise mechanism of the action of the suggested positive effect of glucosamine or glucosamine sulphate on cartilage proteoglycans is not known, since the level of glucosamine in plasma remains very low after oral administration of glucosamine sulphate. We examined whether exogenous hexosamines or their sulphated forms would increase steady-state levels of aggrecan and hyaluronan synthase (HAS) or glycosaminoglycan synthesis using Northern blot and (35)S-sulphate incorporation analyses. Total RNA was extracted from bovine primary chondrocytes which were cultured either in 1 mM concentration of glucosamine, galactosamine, mannosamine, glucosamine 3-sulphate, glucosamine 6-sulphate or galactosamine 6-sulphate for 0, 4, 8 and 24 h, or in three different concentrations (control, 100 microM and 1 mM) of glucosamine sulphate salt or glucose for 24 or 72 h. Northern blot assay showed that neither hexosamines nor glucosamine sulphate salt stimulated aggrecan and HAS-2 mRNA expression. Glycosaminoglycan synthesis remained at a control level in the treated cultures, with the exception of mannosamine which inhibited (35)S-sulphate incorporation in low-glucose DMEM treatment. In our culture conditions, hexosamines or their sulphated forms did not increase aggrecan expression or (35)S-sulphate incorporation.

  • 25.
    Salami, Alireza
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Eriksson, Johan
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Nilsson, Lars-Göran
    Stockholm University.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Age-related white matter microstructural differences partly mediate age-related decline in processing speed but not cognition2012In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1822, no 3, p. 408-415Article in journal (Refereed)
    Abstract [en]

    Aging is associated with declining cognitive performance as well as structural changes in brain gray and white matter (WM). The WM deterioration contributes to a disconnection among distributed brain networks and may thus mediate age-related cognitive decline. The present diffusion tensor imaging (DTI) study investigated age-related differences in WM microstructure and their relation to cognition (episodic memory, visuospatial processing, fluency, and speed) in a large group of healthy subjects (n=287) covering 6 decades of the human life span. Age related decreases in fractional anisotropy (FA) and increases in mean diffusivity (MD) were observed across the entire WM skeleton as well as in specific WM tracts, supporting the WM degeneration hypothesis. The anterior section of the corpus callosum was more susceptible to aging compared to the posterior section, lending support to the anterior-posterior gradient of WM integrity in the corpus callosum. Finally, and of critical interest, WM integrity differences were found to mediate age-related reductions in processing speed but no significant mediation was found for episodic memory, visuospatial ability, or fluency. These findings suggest that compromised WM integrity is not a major contributing factor to declining cognitive performance in normal aging. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.

  • 26.
    Shevela, Dmitriy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Probing the turnover efficiency of photosystem II membrane fragments with different electron acceptors2012In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1817, no 8, p. 1208-1212Article in journal (Refereed)
    Abstract [en]

    In this study we employ isotope ratio membrane-inlet mass spectrometry to probe the turnover efficiency of photosystem II (PSII) membrane fragments isolated from spinach at flash frequencies between 1Hz and 50Hz in the presence of the commonly used exogenous electron acceptors potassium ferricyanide(III) (FeCy), 2,5-dichloro-p-benzoquinone (DCBQ), and 2-phenyl-p-benzoquinone (PPBQ). The data obtained clearly indicate that among the tested acceptors PPBQ is the best at high flash frequencies. If present at high enough concentration, the PSII turnover efficiency is unaffected by flash frequency of up to 30Hz, and at 40Hz and 50Hz only a slight decrease by about 5-7% is observed. In contrast, drastic reductions of the O(2) yields by about 40% and 65% were found at 50Hz for DCBQ and FeCy, respectively. Comparison with literature data reveals that PPBQ accepts electrons from Q(A)(-) in PSII membrane fragments with similar efficiency as plastoquinone in intact cells. Our data also confirm that at high flashing rates O(2) evolution is limited by the reactions on the electron-acceptor side of PSII. The relevance of these data to the evolutionary development of the water-splitting complex in PSII and with regard to the potential of artificial water-splitting catalysts is discussed. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial Photosynthesis.

  • 27.
    Shi, Lan-Xin
    et al.
    Department of Plant Biology, University of California-Davis, USA.
    Hall, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Funk, Christiane
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Schröder, Wolfgang P
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Photosystem II, a growing complex: Updates on newly discovered components and low molecular mass proteins2012In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1817, no 1, p. 13-25Article in journal (Refereed)
    Abstract [en]

    Photosystem II is a unique complex capable of absorbing light and splitting water. The complex has been thoroughly studied and to date there are more than 40 proteins identified, which bind to the complex either stably or transiently. Another special feature of this complex is the unusually high content of low molecular mass proteins that represent more than half of the proteins. In this review we summarize the recent findings on the low molecular mass proteins (<15 kDa) and present an overview of the newly identified components as well. We have also performed co-expression analysis of the genes encoding PSII proteins to see if the low molecular mass proteins form a specific sub-group within the Photosystem II complex. Interestingly we found that the chloroplast-localized genes encoding PSII proteins display a different response to environmental and stress conditions compared to the nuclear localized genes. This article is part of a Special Issue entitled: Photosystem II.

     

  • 28.
    Shingler, V
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Thomas, C M
    Analysis of nonpolar insertion mutations in the trfA gene of IncP plasmid RK2 which affect its broad-host-range property.1989In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1007, no 3Article in journal (Refereed)
    Abstract [en]

    Replication of broad-host-range plasmid RK2 requires the protein product(s) of the plasmid-encoded trfA gene to initiate replication at oriV, the vegetative replication origin. The trfA gene contains two translational starts which direct translation of two polypeptides, of 382 and 285 amino acids, which differ by the 97 amino acids at their N-terminus. Nonpolar insertions which abolish expression of the larger TrfA polypeptide but otherwise retain the trfA gene's normal expression signals severely reduce plasmid replication efficiency in Pseudomonas aeruginosa and to a lesser extent in Pseudomonas putida, but have very little effect in Escherichia coli. This indicates that the organization of the trfA gene, producing two polypeptides products, plays an important part in the broad-host-range of plasmid RK2 by providing a degree of flexibility in the way the plasmid's replication system interacts with host biochemistry.

  • 29.
    Sironen, Reijo
    et al.
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Karjalainen, Hannu
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Elo, Mika
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Kaarniranta, Kai
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Törrönen, Kari
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Takigawa, Masaharu
    Department of Biochemistry and Molecular Dentistry, Okayama University Dental School, Okayama, Japan.
    Helminen, Heikki
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Lammi, Mikko
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    cDNA array reveals mechanosensitive genes in chondrocytic cells under hydrostatic pressure.2002In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1591, no 1-3, p. 45-54, article id 12183054Article in journal (Refereed)
    Abstract [en]

    Hydrostatic pressure (HP) has a profound effect on cartilage metabolism in normal and pathological conditions, especially in weight-bearing areas of the skeletal system. As an important component of overall load, HP has been shown to affect the synthetic capacity and well-being of chondrocytes, depending on the mode, duration and magnitude of pressure. In this study we examined the effect of continuous HP on the gene expression profile of a chondrocytic cell line (HCS-2/8) using a cDNA array containing 588 well-characterized human genes under tight transcriptional control. A total of 51 affected genes were identified, many of them not previously associated with mechanical stimuli. Among the significantly up-regulated genes were immediate-early genes, and genes involved in heat-shock response (hsp70, hsp40, hsp27), and in growth arrest (GADD45, GADD153, p21(Cip1/Waf1), tob). Markedly down-regulated genes included members of the Id family genes (dominant negative regulators of basic helix-loop-helix transcription factors), and cytoplasmic dynein light chain and apoptosis-related gene NIP3. These alterations in the expression profile induce a transient heat-shock gene response and activation of genes involved in growth arrest and cellular adaptation and/or differentiation.

  • 30.
    Ström, Anna-Lena
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Medical and Clinical Genetics.
    Forsgren, Lars
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Holmberg, Monica
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Medical and Clinical Genetics.
    Identification and characterization of Spinocerebellar Ataxia Type 7 (SCA7) isoform SCA7b in mice2005In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1731, no 3, p. 149-153Article in journal (Refereed)
    Abstract [en]

    Spinocerebellar ataxia type 7 (SCA7) is a neurodegenerative disease primarily affecting the cerebellum, brainstem and retina. The disease is caused by a polyglutamine expansion in ataxin-7, a protein with largely unknown function. To improve our knowledge of the expression and function of wild-type and expanded ataxin-7, we looked for alternative SCA7 transcripts in mice. We identified a murine SCA7 isoform (SCA7b) containing an uncharacterized exon homologous to the newly identified human exon 12b. Northern blot analysis revealed three exon 12b containing transcripts with molecular sizes of 7.5, 4.4 and 3.0 kb in mice. This contrasted with the situation in humans, where only one exon 12b-containing transcript was observed. Furthermore, Northern blot of the human 4.4 kb SCA7b isoform predominantly showed expression in the brain, while expression of both the murine 7.5-kb and the 4.4-kb transcripts were observed in several tissues including brain, heart, liver, kidney and testis. Quantitative real-time RT-PCR analysis revealed that in muscle and heart SCA7b is the predominant SCA7 isoform, while in brain equal levels of SCA7a and SCA7b was observed. Insertion of exon 12b into the murine SCA7 ORF resulted in a frame-shift that gave rise to an alternative ataxin-7 protein (ataxin-7b). The novel 58-amino acid C-terminus in ataxin-7b directed the protein to a more cytoplasmic location.

  • 31. Su, Ji-Hu
    et al.
    Cox, Nicholas
    Ames, William
    Pantazis, Dimitrios A
    Rapatskiy, Leonid
    Lohmiller, Thomas
    Kulik, Leonid V
    Dorlet, Pierre
    Rutherford, A William
    Neese, Frank
    Boussac, Alain
    Lubitz, Wolfgang
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The electronic structures of the S(2) states of the oxygen evolving complexes of photosystem II in plants and cyanobacteria in the presence and absence of methanol2011In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1807, no 7, p. 829-840Article in journal (Refereed)
    Abstract [en]

    The electronic properties of the Mn(4)O(x)Ca cluster in the S(2) state of the oxygen evolving complex (OEC) were studied using X- and Q-band EPR and Q-band (55)Mn-ENDOR using photosystem II preparations isolated from the thermophilic cyanobacterium T. elongatus and higher plants (spinach). The data presented here show that there is very little difference between the two species. Specifically it is shown that: (i) only small changes are seen in the fitted isotropic hyperfine values, suggesting that there is no significant difference in the overall spin distribution (electronic coupling scheme) between the two species; (ii) the inferred fine-structure tensor of the only Mn(III) ion in the cluster is of the same magnitude and geometry for both species types, suggesting that the Mn(III) ion has the same coordination sphere in both sample preparations; and (iii) the data from both species are consistent with only one structural model available in the literature, namely the Siegbahn structure [Siegbahn, P. E. M. Accounts Chem. Res.2009, 42, 1871-1880, Pantazis, D. A. et al., Phys. Chem. Chem. Phys.2009, 11, 6788-6798]. These measurements were made in the presence of methanol because it confers favorable magnetic relaxation properties to the cluster that facilitate pulse-EPR techniques. In the absence of methanol the separation of the ground state and the first excited state of the spin system is smaller. For cyanobacteria this effect is minor but in plant PS II it leads to a break-down of the S(T)=½ spin model of the S(2) state. This suggests that the methanol-OEC interaction is species dependent. It is proposed that the effect of small organic solvents on the electronic structure of the cluster is to change the coupling between the outer Mn (Mn(A)) and the other three Mn ions that form the trimeric part of the cluster (Mn(B), Mn(C), Mn(D)), by perturbing the linking bis-μ-oxo bridge. The flexibility of this bridging unit is discussed with regard to the mechanism of O-O bond formation.

  • 32.
    Svenson, Ulrika
    et al.
    Umeå University, Faculty of Medicine, Medical Biosciences, Pathology.
    Roos, Göran
    Umeå University, Faculty of Medicine, Medical Biosciences, Pathology.
    Telomere length as a biological marker in malignancy.2009In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1792, no 4, p. 317-323Article in journal (Refereed)
    Abstract [en]

    Telomere maintenance is important for tumor cell growth and survival. Telomere length (TL) is determined by the balance between positive and negative factors impacting telomere homeostasis. In the last decade, TL has emerged as a promising clinical marker for risk and prognosis prediction in patients with malignant disorders. Tumor TL, as well as TL in healthy tissues such as peripheral blood, may carry valuable information for future treatment strategies. Here we discuss the present status of TL as a biological marker in cancer patients.

  • 33. Szilágyi, Anna
    et al.
    Selstam, Eva
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Åkerlund, Hans-Erik
    Laurdan fluorescence spectroscopy in the thylakoid bilayer: The effect of violaxanthin to zeaxanthin conversion on the galactolipid dominated lipid environment.2008In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1778, no 1, p. 348-355Article in journal (Refereed)
    Abstract [en]

    Laurdan (6-lauroyl-2-dimethylaminonaphthalene) fluorescence spectroscopy has been applied to probe the physical status of the thylakoid membrane upon conversion of violaxanthin to zeaxanthin. So far, only phospholipid-dominated membranes have been studied by this method and hereby we report the first use of laurdan in mono- and digalactosyldiacylglycerol-dominated membrane systems. The generalised polarisation (GP) of laurdan was used as a measure of the structural effect of xanthophyll cycle pigments in isolated spinach (Spinacia oleracea) thylakoids and in model membrane vesicles composed of chloroplast galactolipids. Higher GP values indicate a membrane in a more ordered structure, whereas lower GP values point to a membrane in a less ordered fluid phase. The method was used to probe the effect of violaxanthin and zeaxanthin in thylakoid membranes at different temperatures. At 4, 25 and 37 °C the GP values for dark-adapted thylakoids in the violaxanthin-form were 0.55, 0.28 and 0.26. After conversion of violaxanthin to zeaxanthin, at the same temperatures, the GP values were 0.62, 0.36 and 0.34, respectively. GP values increased gradually upon conversion of violaxanthin to zeaxanthin. Similar results were obtained in the liposomal systems in the presence of these xanthophyll cycle pigments. We conclude from these results that the conversion of violaxanthin to zeaxanthin makes the thylakoid membrane more ordered.

  • 34. Szilágyi, Anna
    et al.
    Sommarin, Marianne
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Akerlund, Hans-Erik
    Membrane curvature stress controls the maximal conversion of violaxanthin to zeaxanthin in the violaxanthin cycle--influence of alpha-tocopherol, cetylethers, linolenic acid, and temperature.2007In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1768, no 9, p. 2310-8Article in journal (Refereed)
    Abstract [en]

    Zeaxanthin, an important component in protection against overexcitation in higher plants, is formed from violaxanthin by the enzyme violaxanthin de-epoxidase. We have investigated factors that may control the maximal degree of conversion in the violaxanthin cycle. The conversion of violaxanthin to zeaxanthin in isolated spinach thylakoids was followed at different temperatures and in the presence of lipid packing modifiers. The maximum degree of conversion was found to be 35%, 70% and 80% at 4 degrees C, 25 degrees C and 37 degrees C respectively. In the presence of membrane modifying agents, known to promote non-lamellar structures (H(II)), such as linolenic acid the conversion increased, and the maximal level of violaxanthin de-epoxidation obtained was close to 100%. In contrast, substances promoting lamellar phases (L(alpha)), such as alpha-tocopherol and 8-cetylether (C(16)EO(8)), only 55% and 35% of the violaxanthin was converted at 25 degrees C, respectively. The results are interpreted in light of the lipid composition of the thylakoid membrane, and we propose a model where a negative curvature elastic stress in the thylakoid lipid bilayer is required for violaxanthin de-epoxidase activity. In this model zeaxanthin with its longer hydrophobic stretch is proposed to promote lamellar arrangements of the membrane. As a result, zeaxanthin relieves the curvature elastic stress, which in turn leads to inactivation of violaxanthin de-epoxidase.

  • 35. Urano, T
    et al.
    Serizawa, K
    Takada, Y
    Ny, Tor
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Takada, A
    Heparin and heparan sulfate enhancement of the inhibitory activity of plasminogen activator inhibitor type 1 toward urokinase type plasminogen activator.1994In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1201, no 2, p. 217-22Article in journal (Refereed)
    Abstract [en]

    To study effects of glycosaminoglycan on the interaction between two chain urokinase type plasminogen activator (tcu-PA) (EC 3.4.21.31) and plasminogen activator inhibitor type 1 (PAI-1) the second order rate constant (k1) between high molecular weight tcu-PA and active recombinant prokaryotic PAI-1 (rpPAI-1) was determined employing a continuous method using chromogenic substrate S-2444 either in the presence or absence of various kinds of glycosaminoglycans. k1 was (5.9 +/- 1.6).10(6)/mol per s in the absence of effector molecule, and following addition of heparin (1.0 U/ml) k1 was enhanced to (3.22 +/- 0.73).10(7). A significant enhancement of k1 was also obtained by heparan sulfate (1.87 +/- 0.25).10(7). Dermatan sulfate or chondroitin sulfate did not show a significant effect on k1 although a slight decrease was obtained by mono-dextran sulfate (4.2 +/- 1.2).10(6). The intrinsic fluorescence of rpPAI-1 was shown to be slightly increased following addition of heparin (1.49 +/- 0.22%, n = 6), suggesting that heparin may enhance the inhibitory activity of PAI-1 toward tcu-PA both by a template mechanism and by a modification of PAI-1 structure.

  • 36. WIESLANDER, A
    et al.
    Selstam, Eva
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    ACYL-CHAIN-DEPENDENT INCORPORATION OF CHLOROPHYLL AND CHOLESTEROL IN MEMBRANES OF ACHOLEPLASMA-LAIDLAWII1987In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 901, no 2, p. 250-254Article in journal (Refereed)
  • 37. Wilson, Sara I
    et al.
    Phylip, L H
    Mills, J S
    Gulnik, S V
    Erickson, J W
    Dunn, B M
    Kay, J
    Escape mutants of HIV-1 proteinase: enzymic efficiency and susceptibility to inhibition1997In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1339, no 1, p. 113-125Article in journal (Refereed)
    Abstract [en]

    Genes encoding a number of mutants of HIV-1 proteinase were sub-cloned and expressed in E. coli. The proteinases containing mutations of single residues (e.g., G48V, V82F, I84V and L90M) were purified and their catalytic efficiencies relative to that of wild-type proteinase were examined using a polyprotein (recombinant HIV-1 gag) substrate and several series of synthetic peptides based on the -Hydrophobic * Hydrophobic-, -Aromatic * Pro- and pseudo-symmetrical types of cleavage junction. The L90M proteinase showed only small changes, whereas the activity of the other mutant enzymes was compromised more severely, particularly towards substrates of the -Aromatic * Pro- and pseudo-symmetrical types. The susceptibility of the mutants and the wild-type proteinase to inhibition by eleven different compounds was compared. The L90M proteinase again showed only marginal changes in its susceptibility to all except one of the inhibitors examined. The K(i) values determined for one inhibitor (Ro31-8959) showed that its potency towards the V82F, L90M, I84V and G48V mutant proteinases respectively was 2-, 3-, 17- and 27-fold less than against the wild-type proteinase. Several of the other inhibitors examined form a systematic series with Ro31-8959. The inhibition constants derived with these and a number of other inhibitors, including ABT-538 and L-735,524, are used in conjunction with the data on enzymic efficiency to assess whether each mutation in the proteinase confers an advantage for viral replication in the presence of any given inhibitor.

  • 38. Yu, Z W
    et al.
    Burén, Jonas
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Enerbäck, S
    Nilsson, E
    Samuelsson, L
    Eriksson, J W
    Insulin can enhance GLUT4 gene expression in 3T3-F442A cells and this effect is mimicked by vanadate but counteracted by cAMP and high glucose--potential implications for insulin resistance.2001In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1535, no 2, p. 174-85Article in journal (Refereed)
    Abstract [en]

    It is well-established that high levels of cAMP or glucose can produce insulin resistance. The aim of this study was to characterize the interaction between these agents and insulin with respect to adipose tissue/muscle glucose transporter isoform (glucose transporter 4, GLUT4) gene regulation in cultured 3T3-F442A adipocytes and to further elucidate the GLUT4-related mechanisms in insulin resistance. Insulin (10(4) microU/ml) treatment for 16 h clearly increased GLUT4 mRNA level in cells cultured in medium containing 5.6 mM glucose but not in cells cultured in medium with high glucose (25 mM). 8-Bromo-cAMP (1 or 4 mM) or N(6)-monobutyryl cAMP, a hydrolyzable and a non-hydrolyzable cAMP analog, respectively, markedly decreased the GLUT4 mRNA level irrespective of glucose concentrations. In addition, these cAMP analogs also inhibited the upregulating effect of insulin on GLUT4 mRNA level. Interestingly, the tyrosine phosphatase inhibitor vanadate (1-50 microM) clearly increased GLUT4 mRNA level in a time- and concentration-dependent manner. Furthermore, cAMP-induced inhibition of the insulin effect was also prevented by vanadate. In parallel to the effects on GLUT4 gene expression, both insulin, vanadate and cAMP produced similar changes in cellular GLUT4 protein content and cAMP impaired the effect of insulin to stimulate (14)C-deoxyglucose uptake. In contrast, insulin, vanadate or cAMP did not alter insulin receptor (IR) mRNA or the cellular content of IR protein. In conclusion: (1) Both insulin and vanadate elicit a stimulating effect on GLUT4 gene expression in 3T3-F442A cells, but a prerequisite is that the surrounding glucose concentration is low. (2) Cyclic AMP impairs the insulin effect on GLUT4 gene expression, but this is prevented by vanadate, probably by enhancing the tyrosine phosphorylation of signalling peptides and/or transcription factors. (3) IR gene and protein expression is not altered by insulin, vanadate or cAMP in this cell type. (4) The changes in GLUT4 gene expression produced by cAMP or vanadate are accompanied by similar alterations in GLUT4 protein expression and glucose uptake, suggesting a role of GLUT4 gene expression for the long-term regulation of cellular insulin action on glucose transport.

  • 39.
    Ådén, Jörgen
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wallgren, Marcus
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Storm, Patrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Weise, Christoph
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Christiansen, Alexander
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Schröder, Wolfgang P
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Funk, Christiane
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wolf-Watz, Magnus
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Extraordinary μs-ms backbone dynamics in Arabidopsis thaliana peroxiredoxin Q2011In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1814, no 12, p. 1880-1890Article in journal (Refereed)
    Abstract [en]

    Peroxiredoxin Q (PrxQ) isolated from Arabidopsis thaliana belongs to a family of redox enzymes called peroxiredoxins, which are thioredoxin- or glutaredoxin-dependent peroxidases acting to reduce peroxides and in particular hydrogen peroxide. PrxQ cycles between an active reduced state and an inactive oxidized state during its catalytic cycle. The catalytic mechanism involves a nucleophilic attack of the catalytic cysteine on hydrogen peroxide to generate a sulfonic acid intermediate with a concerted release of a water molecule. This intermediate is subsequently relaxed by the reaction of a second cysteine, denoted the resolving cysteine, generating an intramolecular disulfide bond and release of a second water molecule. PrxQ is recycled to the active state by a thioredoxin-dependent reduction. Previous structural studies of PrxQ homologues have provided the structural basis for the switch between reduced and oxidized conformations. Here, we have performed a detailed study of the activity, structure and dynamics of PrxQ in both the oxidized and reduced states. Reliable and experimentally validated structural models of PrxQ in both oxidation states were generated using homology based modeling. Analysis of NMR spin relaxation rates shows that PrxQ is monomeric in both oxidized and reduced states. As evident from R(2) relaxation rates the reduced form of PrxQ undergoes unprecedented dynamics on the slow μs-ms timescale. The ground state of this conformational dynamics is likely the stably folded reduced state as implied by circular dichroism spectroscopy. We speculate that the extensive dynamics is intimately related to the catalytic function of PrxQ.

  • 40. Öhman, Anders
    et al.
    Lycksell, P O
    Andell, S
    Langel, U
    Bartfai, T
    Gräslund, A
    Solvent stabilized solution structures of galanin and galanin analogs, studied by circular dichroism spectroscopy.1995In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1236, no 2Article in journal (Refereed)
    Abstract [en]

    Circular dichroism spectroscopy has been used to study how different solvents stabilize secondary structure in the neuropeptide galanin (rat), two N-terminal fragments of galanin, galanin(1-12) and galanin(1-16), and six other differently charged analogs. Among these analogs, the peptide M40, galanin(1-13)-Pro-Pro-Ala-Leu-Ala-Leu-Ala amide, is a high affinity, receptor subtype specific galanin receptor antagonist. The different solvents include sodium dodecyl sulfate (SDS) micelle solutions, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dioleoyl-sn-glycero-3-phosphoglycerol (DOPG) vesicle solutions. 100% 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) and 100% 2,2,2-trifluoroethanol (TFE). DOPC vesicles did not change the structure of the peptides as compared to aqueous solvent. The negatively charged DOPG vesicles and SDS micelles induced similar changes towards alpha-helical structures in all peptides. The HFP and TFE solvents have an even stronger tendency to stabilize alpha-helical conformations in these peptides. Since DOPG vesicles can be considered as a model system for negatively charged biological membranes, the solution structures observed in the presence of DOPG or SDS may be the most relevant for the in vivo situation. Correlations between the binding affinity of the peptides to hippocampal galanin receptors and their observed structures in the DOPG solvent were investigated.

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