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Localization of the small CAB-like proteins in photosystem II.
Umeå University, Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Science and Technology, Chemistry.
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2007 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, Vol. 282, no 1, 267-276 p.Article in journal (Refereed) Published
Abstract [en]

The cyanobacterial small CAB-like proteins (SCPs) consist of one-helix proteins that resemble transmembrane regions of the light-harvesting proteins of plants. To determine whether these proteins are associated with protein complexes in the thylakoid membrane, an abundant member of the SCP family, ScpD, was marked with a His tag, and proteins co-isolating with His-tagged ScpD were identified. These proteins included the major Photosystem (PS) II components as well as FtsH, which is involved in degradation of the PSII complex. To ascertain specific interaction between ScpD and the PSII complex, the His-tagged protein fraction was subjected to two-dimensional blue native/SDS-PAGE. Again, PSII components were co-isolated with ScpD-His, and ScpD-His was found to interact most strongly with CP47. ScpD association was most prominent with the monomeric form of PSII, suggesting ScpD association with PSII that is repaired. Using antibodies that recognize both ScpC and ScpD, we found the ScpC protein, which is very similar in primary structure to ScpD, to also co-isolate with the PSII complex. In contrast, ScpE did not co-isolate with a major protein complex in thylakoids. A fourth member of the SCP family, ScpB, could not be immunodetected, but was found by mass spectrometry in samples co-isolating with ScpD-His. Therefore, ScpB may be associated with ScpD as well. No association between SCPs and PSI could be demonstrated. On the basis of these and other data presented, we suggest that members of the SCP family can associate with damaged PSII and can serve as a temporary pigment reservoir while PSII components are being replaced.

Place, publisher, year, edition, pages
Free Journals , 2007. Vol. 282, no 1, 267-276 p.
Keyword [en]
Chlorophyll/chemistry, Electrophoresis; Polyacrylamide Gel, Histidine/chemistry, Light-Harvesting Protein Complexes, Models; Biological, Multigene Family, Mutation, Photosynthetic Reaction Center Complex Proteins, Photosystem II Protein Complex, Protein Binding, Protein Structure; Tertiary, Spectrometry; Mass; Matrix-Assisted Laser Desorption-Ionization, Synechocystis/*metabolism
URN: urn:nbn:se:umu:diva-10163DOI: 10.1074/jbc.M605463200PubMedID: 17105726OAI: diva2:149834
Available from: 2007-03-02 Created: 2007-03-02 Last updated: 2009-09-10Bibliographically approved
In thesis
1. The Small Cab-like Proteins in the cyanobacterium Synechocystis sp. PCC 6803
Open this publication in new window or tab >>The Small Cab-like Proteins in the cyanobacterium Synechocystis sp. PCC 6803
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Small Cab-like Proteins (SCPs) in the cyanobacterium Synechocystis sp. PCC 6803 accumulate in cells grown under different stress conditions. Genes coding for SCPs have been found in all sequenced organisms performing oxygenic photosynthesis and even in the genomes of cyanophages. Deletion of multiple scp genes in Synechocystis resulted in mutants with severely impaired growth and altered pigment content. These findings indicate the importance of SCPs in photosynthesis; however, their specific function is not well understood. SCPs share a chlorophyll-binding motif with the plant light harvesting complex, suggesting that they bind chlorophyll. Here I describe my findings, which unambiguously show that SCPs are able to bind chlorophyll in vitro. Although they affect both the stoichiometric ratio of Photosystem I to II and chlorophyll stability, they do not seem to be directly involved in non-photochemical quenching. I was able to reveal the location of the SCPs within the cyanobacterial cell: in stressed cells they attach to Photosystem II in the thylakoid membrane. Furthermore, I revealed the presence of another light-harvesting like (Lil)/SCP protein in Synechocystis sp. PCC 6803. The gene, slr1544, codifying for this newly characterised LilA protein, co-transcribes together with scpD and also appears to bind to Photosystem II during stress.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2009. 49 p.
Photosynthesis, Photosystem II, chlorophyll-binding proteins, tetrapyrrole biosynthesis, photodamage, non-photochemical quenching, SCPs, LHCII
National Category
Biochemistry and Molecular Biology Botany
Research subject
urn:nbn:se:umu:diva-25886 (URN)978-91-7264-849-4 (ISBN)
Kemi, 90187, Umeå
Public defence
2009-10-02, KB3B9, KBChuset, Umeå Universitet, Umeå, 13:00 (English)
Available from: 2009-09-11 Created: 2009-09-09 Last updated: 2009-09-11Bibliographically approved

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