umu.sePublications
Change search
Link to record
Permanent link

Direct link
BETA
Sethson, Ingmar
Publications (10 of 18) Show all publications
Siedlecka, A., Wiklund, S., Peronne, M.-A., Micheli, F., Lesniewska, J., Sethson, I., . . . Mellerowicz, E. J. (2008). Pectin methyl esterase inhibits intrusive and symplastic cell growth in developing wood cells of Populus. Plant Physiology, 146, 554-65
Open this publication in new window or tab >>Pectin methyl esterase inhibits intrusive and symplastic cell growth in developing wood cells of Populus
Show others...
2008 (English)In: Plant Physiology, ISSN 0032-0889, Vol. 146, p. 554-65Article in journal (Refereed) Published
Abstract [en]

Wood cells, unlike most other cells in plants, grow by a unique combination of intrusive and symplastic growth. Fibers grow in diameter by diffuse symplastic growth, but they elongate solely by intrusive apical growth penetrating the pectin-rich middle lamella that cements neighboring cells together. In contrast, vessel elements grow in diameter by a combination of intrusive and symplastic growth. We demonstrate that an abundant pectin methyl esterase (PME, EC 3.1.1.11) from wood-forming tissues of hybrid aspen (Populus tremula L. x tremuloides Michx.) acts as a negative regulator of both symplastic and intrusive growth of developing wood cells. When PttPME1expression was up- and down-regulated in transgenic aspen trees, the PME activity in wood-forming tissues was correspondingly altered. PME removes methyl ester groups from homogalacturonan, and the transgenic trees had modified homogalacturonan methylesterification patterns, as demonstrated by two-dimensional NMR and immunostaining using PAM1 and LM7 antibodies. The in situ distributions of PAM1 and LM7 epitopes revealed changes in pectin methylesterification in the transgenic trees that were specifically localized in expanding wood cells. The results show that en-block de-esterification of homogalacturonan by PttPME1 inhibits both symplastic growth and intrusive growth. PttPME1 is therefore involved in mechanisms determining fiber width and length in the wood of aspen trees.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-6462 (URN)10.1104/pp.107.111963 (DOI)18065553 (PubMedID)
Available from: 2008-02-12 Created: 2008-02-12 Last updated: 2018-06-09Bibliographically approved
Wågberg, T., Hedenström, M., Talyzin, A. V., Sethson, I., Tsybin, Y. O., Purcell, J. M., . . . Johnels, D. (2008). Synthesis and Structural Characterization of C70H38. Angewandte Chemie International Edition, 47(15), 2796-9
Open this publication in new window or tab >>Synthesis and Structural Characterization of C70H38
Show others...
2008 (English)In: Angewandte Chemie International Edition, Vol. 47, no 15, p. 2796-9Article in journal (Refereed) Published
Keywords
fullerenes, hydrogenation, mass spectrometry, NMR spectroscopy, reaction mechanism
Identifiers
urn:nbn:se:umu:diva-9505 (URN)10.1002/anie.200705450 (DOI)
Note

Funded by: USA National Science Foundation; Grant Number: DMR-0084173, Florida State University National High Magnetic Field Laboratory in Tallahasse, FL

Available from: 2008-04-14 Created: 2008-04-14 Last updated: 2018-06-09Bibliographically approved
Brorsson, A.-C., Lundqvist, M., Sethson, I. & Jonsson, B.-H. (2006). GuHCl and NaCl-dependent hydrogen exchange in MerP reveals a well-defined core with an unusual exchange pattern. Journal of Molecular Biology, 357(5), 1634-46
Open this publication in new window or tab >>GuHCl and NaCl-dependent hydrogen exchange in MerP reveals a well-defined core with an unusual exchange pattern
2006 (English)In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 357, no 5, p. 1634-46Article in journal (Refereed) Published
Abstract [en]

We have analysed hydrogen exchange at amide groups to characterise the energy landscape of the 72 amino acid residue protein MerP. From the guanidine hydrochloride (GuHCl) dependence of exchange in the pre-transitional region we have determined free energy values of exchange (DeltaG(HX)) and corresponding m-values for individual amide protons. Detailed analysis of the exchange patterns indicates that for one set of amide protons there is a weak dependence on denaturant, indicating that the exchange is dominated by local fluctuations. For another set of amide protons a linear, but much stronger, denaturant dependence is observed. Notably, the plots of free energy of exchange versus [GuHCl] for 16 amide protons show pronounced upward curvature, and a close inspection of the structure shows that these residues form a well-defined core in the protein. The hydrogen exchange that was measured at various concentrations of NaCl shows an apparent selective stabilisation of this core. Detailed analysis of this exchange pattern indicates that it may originate from selective destabilisation of the unfolded state by guanidinium ions and/or selective stabilisation of the core in the native state by chloride ions.

Place, publisher, year, edition, pages
Elsevier Ltd, 2006
Keywords
protein folding, selective stabilisation
Identifiers
urn:nbn:se:umu:diva-20497 (URN)10.1016/j.jmb.2006.01.090 (DOI)16490211 (PubMedID)
Available from: 2009-03-20 Created: 2009-03-20 Last updated: 2018-06-09Bibliographically approved
Lundqvist, M., Sethson, I. & Jonsson, B.-H. (2005). High-resolution 2D 1H-15N NMR characterization of persistent structural alterations of proteins induced by interactions with silica nanoparticles.. Langmuir, 21(13), 5974-9
Open this publication in new window or tab >>High-resolution 2D 1H-15N NMR characterization of persistent structural alterations of proteins induced by interactions with silica nanoparticles.
2005 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 13, p. 5974-9Article in journal (Refereed) Published
Abstract [en]

The binding of protein to solid surfaces often induces changes in the structure, and to investigate these matters we have selected two different protein-nanoparticle systems. The first system concerns the enzyme human carbonic anhydrase II which binds essentially irreversibly to the nanoparticles, and the second system concerns human carbonic anhydrase I which alternate between the adsorbed and free state upon interaction with nanoparticles. Application of the TROSY pulse sequence has allowed high-resolution NMR analysis for both of the protein-nanoparticle systems. For HCAII it was possible to observe spectra of protein when bound to the nanoparticles. The results indicated that HCAII undergoes large rearrangements, forming an ensemble of molten globule-like structures on the surface. The spectra from the HCAI-nanoparticle system are dominated by HCAI molecules in solution. A comparative analysis of variations in intensity from 97 amide resonances in a 1H-15N TROSY spectrum revealed the effects from interaction with nanoparticle on the protein structure at amino acid resolution.

Place, publisher, year, edition, pages
ACS Publications, 2005
Identifiers
urn:nbn:se:umu:diva-20650 (URN)10.1021/la050569j (DOI)15952849 (PubMedID)
Available from: 2009-03-24 Created: 2009-03-24 Last updated: 2018-06-09Bibliographically approved
Hedenström, M., Emtenäs, H., Pemberton, N., Åberg, V., Hultgren, S. J., Pinkner, J. S., . . . Kihlberg, J. (2005). NMR studies of interactions between periplasmic chaperones from uropathogenic E-coli and pilicides that interfere with chaperone function and pilus assembly. ORGANIC & BIOMOLECULAR CHEMISTRY, 3(23), 4193-4200
Open this publication in new window or tab >>NMR studies of interactions between periplasmic chaperones from uropathogenic E-coli and pilicides that interfere with chaperone function and pilus assembly
Show others...
2005 (English)In: ORGANIC & BIOMOLECULAR CHEMISTRY, ISSN 1477-0520, Vol. 3, no 23, p. 4193-4200Article in journal (Refereed) Published
Abstract [en]

Adherence of uropathogenic Escherichia coli to host tissue is mediated by pili, which are hair-like protein structures extending from the outer cell membrane of the bacterium. The chaperones FimC and PapD are key components in pilus assembly since they catalyse folding of subunits that are incorporated in type 1 and P pili, respectively, and also transport the subunits across the periplasmic space. Recently, compounds that inhibit pilus biogenesis and interfere with chaperone-subunit interactions have been discovered and termed pilicides. In this paper NMR spectroscopy was used to study the interaction of different pilicides with PapD and FimC in order to gain structural knowledge that would explain the effect that some pilicides have on pilus assembly. First relaxation-edited NMR experiments revealed that the pilicides bound to the PapD chaperone with mM affinity. Then the pilicide-chaperone interaction surface was investigated through chemical shift mapping using N-15-labelled FimC. Principal component analysis performed on the chemical shift perturbation data revealed the presence of three binding sites on the surface of FimC, which interacted with three different classes of pilicides. Analysis of structure-activity relationships suggested that pilicides reduce pilus assembly in E. coli either by binding in the cleft of the chaperone, or by influencing the orientation of the flexible F1-G1 loop, both of which are part of the surface by which the chaperone forms complexes with pilus subunits. It is suggested that binding to either of these sites interferes with folding of the pilus subunits, which occurs during formation of the chaperone-subunit complexes. In addition, pilicides that influence the F1-G1 loop also appear to reduce pilus formation by their ability to dissociate chaperone-subunit complexes.

Keywords
RING-FUSED 2-PYRIDINONES, SOLID-PHASE SYNTHESIS, STRUCTURAL BASIS, PATHOGENIC BACTERIA, SUBUNIT RECOGNITION, PAPD CHAPERONE, RNA-BINDING, TYPE-1 PILI, PROTEIN, ADHESIN
Identifiers
urn:nbn:se:umu:diva-13585 (URN)10.1039/b511857c (DOI)
Available from: 2007-06-14 Created: 2007-06-14 Last updated: 2018-06-09Bibliographically approved
Berglund, A., Brorsson, A.-C., Jonsson, B.-H. & Sethson, I. (2005). The equilibrium unfolding of MerP characterized by multivariate analysis of 2D NMR data. Journal of magnetic resonance, 172(1), 24-30
Open this publication in new window or tab >>The equilibrium unfolding of MerP characterized by multivariate analysis of 2D NMR data
2005 (English)In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 172, no 1, p. 24-30Article in journal (Refereed) Published
Abstract [en]

A general problem when analysing NMR spectra that reflect variations in the environment of target molecules is that different resonances are affected to various extents. Often a few resonances that display the largest frequency changes are selected as probes to reflect the examined variation, especially in the case, where the NMR spectra contain numerous resonances. Such a selection is dependent on more or less intuitive judgements and relying on the observed spectral variation being primarily caused by changes in the NMR sample. Second, recording changes observed for a few (albeit significant) resonances is inevitably accompanied by not using all available information in the analysis. Likewise, the commonly used chemical shift mapping (CSM) [Biochemistry 39 (2000) 26, Biochemistry 39 (2000) 12595] constitutes a loss of information since the total variation in the data is not retained in the projection into this single variable. Here, we describe a method for subjecting 2D NMR time-domain data to multivariate analysis and illustrate it with an analysis of multiple NNIR experiments recorded at various folding conditions for the protein MerP. The calculated principal components provide an unbiased model of variations in the NNIR spectra and they can consequently be processed as NMR data, and all the changes as reflected in the principal components are thereby made available for visual inspection in one single NMR spectrum. This approach is much less laborious than consideration of large numbers of individual spectra, and it greatly increases the interpretative power of the analysis.

Place, publisher, year, edition, pages
San Diego: Academic Press, 2005
Keywords
multivariate NMR data analysis, protein folding, PCA, PLS, GuHCl
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-13508 (URN)10.1016/j.jmr.2004.09.010 (DOI)000226176800004 ()
Available from: 2007-05-25 Created: 2007-05-25 Last updated: 2018-06-09Bibliographically approved
Lundqvist, M., Sethson, I. & Jonsson, B.-H. (2005). Transient Interaction with Nanoparticles "Freezes" a Protein in an Ensemble of Metastable Near-Native Conformations. Biochemistry including biophysical chemistry& molecular biology, 44(30), 10093-9
Open this publication in new window or tab >>Transient Interaction with Nanoparticles "Freezes" a Protein in an Ensemble of Metastable Near-Native Conformations
2005 (English)In: Biochemistry including biophysical chemistry& molecular biology, Vol. 44, no 30, p. 10093-9Article in journal (Refereed) Published
Abstract [en]

 

It is well-known that adsorption of proteins on interfaces often induces substantial alterations of the protein structure. However, very little is known about whether these conformational changes have any consequence for the protein conformation after desorption from the interface. To investigate this matter, we have selected a protein-particle system in which the enzyme human carbonic anhydrase I (HCAI) alternates between the adsorbed and free state upon interaction with the silica nanoparticles. High-resolution NMR analysis of the protein with the particles present in the sample shows a spectrum that indicates a molten globular-like structure. Removal of particles results in refolding of virtually all HCAI molecules to a fully active form. However, the two-dimensional NMR analysis shows that refolding does not result in a single well-defined protein structure but rather provides an ensemble of protein molecules with near-native conformations. A detailed comparative chemical shift analysis of 108 amide signals in 1H-15N HSQC spectra of native and desorbed HCAI reveals that the most profound effects are located at β-strands in the center of the molecule. The observation of very slow H-D exchange in the central β-strands of HCAI [Kjellsson, A., Sethson, I., and Jonsson, B. H. (2003) Biochemistry 42, 363-374] in conjunction with our results indicates that the kinetic barriers for conformational rearrangements in the central core of the protein are low in the presence of nanoparticles but are very high under native conditions.

Place, publisher, year, edition, pages
ACS Publications, 2005
Identifiers
urn:nbn:se:umu:diva-22981 (URN)10.1021/bi0500067 (DOI)
Available from: 2009-05-25 Created: 2009-05-25 Last updated: 2018-06-08Bibliographically approved
Berglund, A. & Sethson, I. (2004). Analysis of 2D-NMR data in the time domain, a study of the unfolding of MERP. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 228(1), U111-U111
Open this publication in new window or tab >>Analysis of 2D-NMR data in the time domain, a study of the unfolding of MERP
2004 (English)In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, ISSN 0065-7727, Vol. 228, no 1, p. U111-U111Article in journal (Other academic) Published
Identifiers
urn:nbn:se:umu:diva-14284 (URN)
Note

Meeting Abstract AUG 22 2004

Available from: 2008-04-17 Created: 2008-04-17 Last updated: 2018-06-09Bibliographically approved
Buevich, A. V., Lundberg, S., Sethson, I., Edlund, U. & Backman, L. (2004). NMR studies of calcium-binding to mutant alpha-spectrin EF-hands. CELLULAR & MOLECULAR BIOLOGY LETTERS, 9(1), 167-86
Open this publication in new window or tab >>NMR studies of calcium-binding to mutant alpha-spectrin EF-hands
Show others...
2004 (English)In: CELLULAR & MOLECULAR BIOLOGY LETTERS, ISSN 1425-8153, Vol. 9, no 1, p. 167-86Article in journal (Refereed) Published
Abstract [en]

The co-operative calcium binding mechanism of the two C-terminal EF-hands of human all-spectrin has been investigated by site-specific mutagenesis and multi-dimensional NMR spectroscopy. To analyse the calcium binding of each EF-hand independently, two mutant structures (E33A and D69S) of wild type alpha-spectrin were prepared. According to NMR analysis both E33A and D69S were properly folded. The unmutated EF-hand in these mutants remained nearly intact and active in calcium binding, whereas the mutated EF-hand lost its affinity for calcium completely. The apparent calcium binding affinity of the E33A mutant was much lower compared to the D39S mutant (similar to2470 muM and similar to240 muM, respectively). When the chemical shift perturbations were followed upon calcium titration, a positive correlation between the D69S mutant and the binding of the first calcium ion to the wild type was revealed. These observations showed that the first EF-hand in spectrin binds the first calcium ion and thereby triggers a conformational change that allows the second calcium ion to bind to the other EF-hand.

Keywords
EF-hand, site-specific mutagenesis, multidimensional NMR
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-14274 (URN)
Available from: 2007-05-28 Created: 2007-05-28 Last updated: 2018-06-09Bibliographically approved
Lundqvist, M., Sethson, I. & Jonsson, B.-H. (2004). Protein adsorption onto silica nanoparticles: Conformational changes depend on the particles' curvature and the protein stability. Langmuir, 20(24), 10639-47
Open this publication in new window or tab >>Protein adsorption onto silica nanoparticles: Conformational changes depend on the particles' curvature and the protein stability
2004 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Langmuir, Vol. 20, no 24, p. 10639-47Article in journal (Refereed) Published
Abstract [en]

We have analyzed the adsorption of protein to the surfaces of silica nanoparticles with diameters of 6, 9, and 15 nm. The effects upon adsorption on variants of human carbonic anhydrase with differing conformational stabilities have been monitored using methods that give complementary information, i.e., circular dichroism (CD), nuclear magnetic resonance (NMR), analytical ultracentrifugation (AUC), and gel permeation chromatography. Human carbonic anhydrase I (HCAI), which is the most stable of the protein variants, establishes a dynamic equilibrium between bound and unbound protein following mixture with silica particles. Gel permeation and AUC experiments indicate that the residence time of HCAI is on the order of approximately 10 min and slowly increases with time, which allows us to study the effects of the interaction with the solid surface on the protein structure in more detail than would be possible for a process with faster kinetics. The effects on the protein conformation from the interaction have been characterized using CD and NMR measurements. This study shows that differences in particle curvature strongly influence the amount of the protein's secondary structure that is perturbed. Particles with a longer diameter allow formation of larger particle-protein interaction surfaces and cause larger perturbations of the protein's secondary structure upon interaction. In contrast, the effects on the tertiary structure seem to be independent of the particles' curvature.

Place, publisher, year, edition, pages
ACS Publications, 2004
Identifiers
urn:nbn:se:umu:diva-20649 (URN)10.1021/la0484725 (DOI)15544396 (PubMedID)
Available from: 2009-03-24 Created: 2009-03-24 Last updated: 2018-06-09Bibliographically approved
Organisations

Search in DiVA

Show all publications