Species-dependence of the redox potential of the primary quinone electron acceptor QA in photosystem II verified by spectroelectrochemistry
Abstract
The redox potentials Em(QA/
) of the primary quinone electron acceptor QA in oxygen-evolving photosystem II complexes of three species were determined by spectroelectrochemistry. The Em(QA/
) values were experimentally found to be −162
±3mV for a higher plant spinach, −171±3mV for a green alga Chlamydomonas reinhardtii and −104±4mV vs. SHE for a red alga Cyanidioschyzon merolae. On the basis of possible deviations for the experimental values, as estimated to differ by 9–29mV from each true value, plausible causes for such remarkable species-dependence of Em(QA/
) are discussed, mainly by invoking the effects of extrinsic subunits on the delicate structural environment around QA.
Abbreviations: PS II, photosystem II, OTTLE, optically transparent thin-layer electrode, MES, 2-[N-morpholino]ethanesulfonic acid, Chl, chlorophyll, QA, primary quinone electron acceptor, Phe, pheophytin, DCMU, diuron, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, DCBQ, 2,6-dichlorobenzoquinone, LHC, light-harvesting complex
Keywords: Photosystem II, Redox potential, Primary quinone electron acceptor QA, Spectroelectrochemistry, Photosynthesis, Electron transfer
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PII: S0014-5793(10)00195-X
doi:10.1016/j.febslet.2010.03.002
© 2010 Federation of European Biochemical Societies
