Species-dependence of the redox potential of the primary quinone electron acceptor QA in photosystem II verified by spectroelectrochemistry

Edited by Peter Brzezinski

Received 28 December 2009; received in revised form 1 March 2010; accepted 1 March 2010. published online 10 March 2010.

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

a Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan

b Department of Life Sciences (Biology), Graduate School of Art and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan

c Department of Biology, Faculty of Science, Tokyo University of Science, Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan

Corresponding author. Fax: +81 3 5452 6331.

PII: S0014-5793(10)00195-X

doi:10.1016/j.febslet.2010.03.002

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