Natural isoforms of the Photosystem II D1 subunit differ in photoassembly efficiency of the water-oxidizing complex
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2016Metadata
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Vinyard, David J.
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Natural isoforms of the Photosystem II D1 subunit differ in photoassembly efficiency of the water-oxidizing complex
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Oxygenic photosynthesis efficiency at increasing solar flux is limited by light-induced damage (photoinhibition) of Photosystem II (PSII), primarily targeting the D1 reaction center subunit. Some cyanobacteria contain two natural isoforms of D1 that function better under low light (D1:1) or high light (D1:2). Herein, rates and yields of photoassembly of the Mn4CaO5 water-oxidizing complex (WOC) from the free inorganic cofactors (Mn2+, Ca2+, water, electron acceptor) and apo-WOC-PSII are shown to differ significantly: D1:1 apo-WOC-PSII exhibits a 2.3-fold faster rate-limiting step of photoassembly and up to seven-fold faster rate to the first light-stable Mn3+ intermediate, IM1*, but with a much higher rate of photoinhibition than D1:2. Conversely, D1:2 apo-WOC-PSII assembles slower but has up to seven-fold higher yield, achieved by a higher quantum yield of charge separation and slower photoinhibition rate. These results confirm and extend previous observations of the two holoenzymes: D1:2-PSII has a greater quantum yield of primary charge separation, faster [P-680 (+) Q (A) (-) ] charge recombination and less photoinhibition that results in a slower rate and higher yield of photoassembly of its apo-WOC-PSII complex. In contrast, D1:1-PSII has a lower quantum yield of primary charge separation, a slower [P-680 (+) Q (A) (-) ] charge recombination rate, and faster photoinhibition that together result in higher rate but lower yield of photoassembly at higher light intensities. Cyanobacterial PSII reaction centers that contain the high- and low-light D1 isoforms can tailor performance to optimize photosynthesis at varying light conditions, with similar consequences on their photoassembly kinetics and yield. These different efficiencies of photoassembly versus photoinhibition impose differential costs for biosynthesis as a function of light intensity.
Patrocinador
National Science Foundation-Chemistry of Life Processes
CHE1213772
U.S. Department of Energy, Consortium for Algal Biofuels Commercialization
DE-EE0003373
Waksman Institute of Microbiology
Aresty Research Center for Undergraduates at Rutgers University
Department of Deference Army Research Office through a National Defense Science and Engineering Graduate
NDSEG - 32CFR168a
National Science Foundation
DGE-0937373
Comision Nacional de Investigacion Cientifica y Tecnologica de Chile (CONICYT)
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Photosynth Res (2016) 128:141–150
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