The terminal reaction cascade of water oxidation: Proton and oxygen release

Autor(en): Clausen, Juergen
Junge, Wolfgang 
Stichwörter: Biochemistry & Molecular Biology; Biophysics; CHARGE RECOMBINATION; CHLOROPHYLL FLUORESCENCE; DONOR SIDE; ELECTRON-TRANSFER; FTIR DIFFERENCE SPECTROSCOPY; Intermediate; Oxygen; PH-DEPENDENCE; Photosynthesis; Photosystem II; PHOTOSYSTEM-II PARTICLES; PROTOLYTIC REACTIONS; Proton release; SYNECHOCYSTIS SP PCC-6803; TYROSINE Y-Z; Water oxidation
Erscheinungsdatum: 2008
Herausgeber: ELSEVIER SCIENCE BV
Journal: BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
Volumen: 1777
Ausgabe: 10
Startseite: 1311
Seitenende: 1318
Zusammenfassung: 
In cyanobacteria, algae and plants Photosystem II produces the oxygen we breathe. Driven and clocked by light quanta, the catalytic Mn4Ca-tyrosine centre accumulates four oxidising equivalents before it abstracts four electrons from water, liberating dioxygen and protons. Aiming at intermediates of the terminal four-electron cascade, we previously have suppressed this reaction by elevating the oxygen pressure, thereby stabilising one redox intermediate. Here, we established a similar suppression by increasing the proton concentration. Data were analysed in terms of only one (peroxy) redox intermediate between the fourfold oxidised Mn4Ca-tyrosine centre and oxygen release. The surprising result was that the release into the bulk of one proton per dioxygen is linked to the first and rate-limiting electron transfer in the cascade rather than to the second which produces free oxygen. The penultimate intermediate might thus be conceived as a fully deprotonated peroxy-moiety. (C) 2008 Elsevier B.V. All rights reserved.
ISSN: 00052728
DOI: 10.1016/j.bbabio.2008.06.009

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