Proton-coupled electron transfer involving tyrosine Z in photosystem II

Henriette Kühne, Gary W Brudvig

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

The O2-evolving complex (OEC) of photosystem II (PSII) catalyzes the oxidation of water to dioxygen. In addition to a tetramanganese-oxo (Mn4) cluster, calcium and chloride ions, the OEC also contains Tyrosine Z (Yz), a redox intermediate in the water oxidation reaction. The redox mechanism employed by Yz is under much debate. Using a novel method to study Yz oxidation based on the kinetic competition with secondary donors, we examine the electron-donation pathways of manganese-depleted PSII over a range of temperature and pH. H/D substitution causes a shift in the onset temperature for Yz oxidation, enabling measurements of lyonium isotope effects. In deuterated samples, the onset temperature for Yz oxidation is upshifted, suggesting that proton movement is a required step. Proton inventory experiments were performed to determine the number of protons that shift during the Yz oxidation reaction. Our findings indicate the movement of a single proton during the rate-liraiting step of the oxidation process. The results presented herein demonstrate a need for proton movement in conjunction with Yz oxidation and support previous proposals that a proton-coupled electron, transfer (PCET) step is necessary for oxidation of Yz. The possible involvement of PCET in the energetics of specific steps in the mechanism of water oxidation is discussed.

Original languageEnglish
Pages (from-to)8189-8196
Number of pages8
JournalJournal of Physical Chemistry B
Volume106
Issue number33
DOIs
Publication statusPublished - Aug 22 2002

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Photosystem II Protein Complex
tyrosine
Tyrosine
Protons
electron transfer
Oxidation
oxidation
protons
Electrons
Water
water
Calcium Chloride
shift
Manganese
Isotopes
isotope effect
Temperature
temperature
proposals
manganese

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Proton-coupled electron transfer involving tyrosine Z in photosystem II. / Kühne, Henriette; Brudvig, Gary W.

In: Journal of Physical Chemistry B, Vol. 106, No. 33, 22.08.2002, p. 8189-8196.

Research output: Contribution to journalArticle

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