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The small CAB-like proteins of the cyanobacterium Synechocystis sp. PCC 6803: Transcriptomic, proteomic and metabolomic analyses reveal new insights into their function
Umeå University, Faculty of Science and Technology, Department of Chemistry. (Christiane Funk)
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The five small CAB-like proteins (ScpA-E) of the cyanobacterium Synechocystis sp. PCC 6803 consist of one transmembrane helix and belong to the light-harvesting like family. While in wild type they are induced by various stresses, in cells with Photosystem I (PSI) -less background the SCPs are constitutively expressed. Here we performed a detailed comparison of a PSI-less control strain with a strain depleted of PSI and all SCPs, with the aim to elucidate the function of the SCPs within Photosystem II. Electron microscopical immages showed a drastic alteration of the cellular organization, visible by a rough surface and few thylakoid membranes in the PSI-less/ScpABCDE- strain. Immunoblots pointed to a decreased amount of PSII per cell volume. Deletion of the scp genes also affected the carbon- and nitrogen-balance and thereby the carbohydrate accumulation at the expenses of protein- and chlorophyll-synthesis as judged by transcriptomic and metabolomic analyses. Our results show that SCPs ensure a correct assembly/repair of PSII and therefore are important for the adaptation to environmental stresses  - especially during the generation of reactive oxygen species.

Keyword [en]
Photosystem II, Synechocystis sp. PCC 6803, small CAB-like proteins, carbon/nitrogen balance, stress adaptation
National Category
Chemical Sciences
URN: urn:nbn:se:umu:diva-59784OAI: diva2:556614
Available from: 2012-09-25 Created: 2012-09-25 Last updated: 2012-09-27
In thesis
1. Functional studies on the Light-harvesting-Like (LiL) Proteins in Cyanobacteria and Cryptophytes
Open this publication in new window or tab >>Functional studies on the Light-harvesting-Like (LiL) Proteins in Cyanobacteria and Cryptophytes
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The light-harvesting like (LiL) proteins are a widely spread group of proteins within photosynthetic organisms. They are membrane proteins composed of one to four transmembrane helices and – in homology to the light-harvesting complexes of algae and higher plants – at least one of these transmembrane helices contains the chlorophyll a/b-binding (CAB) domain. Opposite to the light-harvesting antenna complexes, LiL proteins are stress induced and they have been shown to be involved in protection of the photosynthetic apparatus. The work presented in this thesis is focused on understanding the function of one-helical LiL proteins of the cryptophyte algae Guillardia theta and the cyanobacterium Synechocystis sp. PCC 6803. G. theta contains two genes encoding LiL proteins, one is localized in the plastid (hlipP), the other in the nucleomorph (HlipNm). Both genes are expressed in normal growth condition, but they are not induced by high light. Immunostaining indicated that HlipNm is translated, but not light-induced. These proteins therefore seem not to be involved in photoprotective mechanisms of G. theta. In the cyanobacterium Synechocystis sp. PCC 6803 four one-helical LiL proteins were identified, they are called Small CAB-like Proteins (SCPs); a fifth LiL (ScpA) is fused with the ferrochelatase (FC), an enzyme involved in the heme synthesis. Our analysis revealed that SCPs are involved in the de novo assembly/repair cycle of Photosystem II, stabilizing the chlorophyll pigments at their protein scaffold. The in vitro characterization of the recombinant FC showed that ScpA is involved in the product-release of the catalytic domain of the enzyme, thereby regulating substrate availability for chlorophyll- or heme- biosynthesis. Finally, using a transcriptomic and metabolomic approaches, I was able to show that deletion of all SCP genes has profound impact on the cell organization and metabolism. In SCP-depleted cells, production of reactive oxygen species (ROS) is increased, while the amount of Photosystem II per cell volume is decreased, causing a macronutrient-deficient phenotype. Therefore, SCPs are important for stress protection and help to maintain a metabolic equilibrium within the cell.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2012. 67 p.
Photosynthesis, cyanobacteria, Guillardia theta, photosystem II, chlorophyll-binding proteins, onehelix LiL proteins, photoprotection
National Category
Natural Sciences
Research subject
urn:nbn:se:umu:diva-59801 (URN)978-91-7459-486-7 (ISBN)
Public defence
2012-10-26, KBC-huset, KB3A9, Umeå University, Umeå, 10:00 (English)
Available from: 2012-10-05 Created: 2012-09-26 Last updated: 2012-09-26Bibliographically approved

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