Document Detail

Natural variants of photosystem II subunit D1 tune photochemical fitness to solar intensity.
MedLine Citation:
PMID:  23271739     Owner:  NLM     Status:  MEDLINE    
Photosystem II (PSII) is composed of six core polypeptides that make up the minimal unit capable of performing the primary photochemistry of light-driven charge separation and water oxidation in all oxygenic phototrophs. The D1 subunit of this complex contains most of the ligating amino acid residues for the Mn(4)CaO(5) core of the water-oxidizing complex (WOC). Most cyanobacteria have 3-5 copies of the psbA gene coding for at least two isoforms of D1, whereas algae and plants have only one isoform. Synechococcus elongatus PCC 7942 contains two D1 isoforms; D1:1 is expressed under low light conditions, and D1:2 is up-regulated in high light or stress conditions. Using a heterologous psbA expression system in the green alga Chlamydomonas reinhardtii, we have measured growth rate, WOC cycle efficiency, and O(2) yield as a function of D1:1, D1:2, or the native algal D1 isoform. D1:1-PSII cells outcompete D1:2-PSII cells and accumulate more biomass in light-limiting conditions. However, D1:2-PSII cells easily outcompete D1:1-PSII cells at high light intensities. The native C. reinhardtii-PSII WOC cycles less efficiently at all light intensities and produces less O(2) than either cyanobacterial D1 isoform. D1:2-PSII makes more O(2) per saturating flash than D1:1-PSII, but it exhibits lower WOC cycling efficiency at low light intensities due to a 40% faster charge recombination rate in the S(3) state. These functional advantages of D1:1-PSII and D1:2-PSII at low and high light regimes, respectively, can be explained by differences in predicted redox potentials of PSII electron acceptors that control kinetic performance.
David J Vinyard; Javier Gimpel; Gennady M Ananyev; Mario A Cornejo; Susan S Golden; Stephen P Mayfield; G Charles Dismukes
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2012-12-27
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  288     ISSN:  1083-351X     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-02-25     Completed Date:  2013-04-25     Revised Date:  2014-02-25    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  5451-62     Citation Subset:  IM    
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MeSH Terms
Chlamydomonas / metabolism
Chlorophyll / metabolism
Cyanobacteria / metabolism
Electron Spin Resonance Spectroscopy
Evolution, Molecular
Fourier Analysis
Genetic Variation
Oxygen / chemistry
Photosynthetic Reaction Center Complex Proteins / chemistry,  metabolism
Photosystem II Protein Complex / genetics*,  physiology*
Protein Isoforms
Solar Energy
Thylakoids / metabolism
Reg. No./Substance:
0/Photosynthetic Reaction Center Complex Proteins; 0/Photosystem II Protein Complex; 0/Protein Isoforms; 1406-65-1/Chlorophyll; S88TT14065/Oxygen

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