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Environmentally modulated phosphoproteome of photosynthetic membranes in the green alga Chlamydomonas reinhardtii
Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
Wolfson Laboratories, Division of Molecular Biosciences, Faculty of Life Sciences, Imperial College London.
Department of Plant Physiology, Umeå University, Umeå, Sweden.
Department of Plant Physiology, Umeå University, Umeå, Sweden.
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2006 (English)In: Molecular & cellular proteomics, ISSN 1535-9476, Vol. 5, no 8, 1412-1425 p.Article in journal (Refereed) Published
Abstract [en]

Mapping of in vivo protein phosphorylation sites in photosynthetic membranes of the green alga Chlamydomonas reinhardtii revealed that the major environmentally dependent changes in phosphorylation are clustered at the interface between the photosystem II (PSII) core and its light-harvesting antennae (LHCII). The photosynthetic membranes that were isolated form the algal cells exposed to four distinct environmental conditions affecting photosynthesis: (i) dark aerobic, corresponding to photosynthetic State 1; (ii) dark under nitrogen atmosphere, corresponding to photosynthetic State 2; (iii) moderate light; and (iv) high light. The surface-exposed phosphorylated peptides were cleaved from the membrane by trypsin, methyl-esterified, enriched by immobilized metal affinity chromatography, and sequenced by nanospray-quadrupole time-of-flight mass spectrometry. A total of 19 in vivo phosphorylation sites were mapped in the proteins corresponding to 15 genes in C. reinhardtii. Amino-terminal acetylation of seven proteins was concomitantly determined. Sequenced amino termini of six mature LHCII proteins differed from the predicted ones. The State 1-to-State 2 transition induced phosphorylation of the PSII core components D2 and PsbR and quadruple phosphorylation of a minor LHCII antennae subunit, CP29, as well as phosphorylation of constituents of a major LHCII complex, Lhcbm1 and Lhcbm10. Exposure of the algal cells to either moderate or high light caused additional phosphorylation of the D1 and CP43 proteins of the PSII core. The high light treatment led to specific hyperphosphorylation of CP29 at seven distinct residues, phosphorylation of another minor LHCII constituent, CP26, at a single threonine, and double phosphorylation of additional subunits of a major LHCII complex including Lhcbm4, Lhcbm6, Lhcbm9, and Lhcbm11. Environmentally induced protein phosphorylation at the interface of PSII core and the associated antenna proteins, particularly multiple differential phosphorylations of CP29 linker protein, suggests the mechanisms for control of photosynthetic state transitions and for LHCII uncoupling from PSII under high light stress to allow thermal energy dissipation.

Place, publisher, year, edition, pages
2006. Vol. 5, no 8, 1412-1425 p.
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-12930DOI: 10.1074/mcp.M600066-MCP200OAI: diva2:17416
Available from: 2008-02-06 Created: 2008-02-06 Last updated: 2009-06-05
In thesis
1. Functional proteomics of protein phosphorylation in algal photosynthetic membranes
Open this publication in new window or tab >>Functional proteomics of protein phosphorylation in algal photosynthetic membranes
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Plants, green algae and cyanobacteria perform photosynthetic conversion of sunlight into chemical energy in the permanently changing natural environment. For successful survival and growth photosynthetic organisms have developed complex sensing and signaling acclimation mechanisms. The environmentally dependent protein phosphorylation in photosynthetic membranes is implied in the adaptive responses; however, the molecular mechanisms of this regulation are still largely unknown. We used a mass spectrometry-based approach to achieve a comprehensive mapping of the in vivo protein phosphorylation sites within photosynthetic membranes from the green alga Chlamydomonas reinhardtii subjected to distinct environmental conditions known to affect the photosynthetic machinery.

The state transitions process regulating the energy distribution between two photosystems, involves the temporal functional coupling of phosphorylated light-harvesting complexes II (LHCII) to photosystem I (PSI). During state transitions several of the thylakoid proteins undergo redox-controlled phosphorylation-dephosphorylation cycles. This work provided evidences suggesting that redox-dependent phosphorylation-induced structural changes of the minor LHCII antenna protein CP29 determine the affinity of LHCII for either of the two photosystems. In state 1 the doubly phosphorylated CP29 acts as a linker between the photosystem II (PSII) core and the trimeric LHCII whereas in state 2 this quadruply phosphorylated CP29 would migrate to PSI on the PsaH side and provide the docking of LHCII trimers to the PSI complex. Moreover, this study revealed that exposure of Chlamydomonas cells to high light stress caused hyperphosphorylation of CP29 at seven distinct residues and suggested that high light-induced hyperphosphorylation of CP29 may uncouple this protein together with LHCII from both photosystems to minimize the damaging effects of excess light.

Reversible phosphorylation of the PSII reaction center proteins was shown to be essential for the maintenance of active PSII under high light stress. Particularly dephosphorylation of the light-damaged D1 protein, a central functional subunit of the PSII reaction center, is required for its degradation and replacement. We found in the alga the reversible D1 protein phosphorylation, which until our work, has been considered as plant-specific.

We also discovered specific induction of thylakoid protein phosphorylation during adaptation of alga to limiting environmental CO2. One of the phosphorylated proteins has five phosphorylation sites at both serine and treonine residues. The discovered specific low-CO2- and redox-dependent protein phosphorylation may be an early adaptive and signalling response of the green alga to limitation in inorganic carbon.

This work provides the first comprehensive insight into the network of environmentally regulated protein phosphorylation in algal photosynthetic membranes.

Place, publisher, year, edition, pages
Linköping University Electronic Press, 2008. 40 p.
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1038
Protein phosphorylation, mass spectrometry, photosynthesis, proteomics
National Category
Biochemistry and Molecular Biology
urn:nbn:se:liu:diva-10708 (URN)978-91-85523-02-3 (ISBN)
Public defence
2008-02-29, Linden, ingång 65, Hälsouniversitetet, Linköping, 13:00 (English)
Available from: 2008-02-06 Created: 2008-02-06 Last updated: 2015-11-19

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