Cation Effects on the Electron-Acceptor Side of Photosystem II

Sahr Khan, Jennifer S. Sun, Gary W Brudvig

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The normal pathway of electron transfer on the electron-acceptor side of photosystem II (PSII) involves electron transfer from quinone A, QA, to quinone B, QB. It is possible to redirect electrons from QA- to water-soluble CoIII complexes, which opens a new avenue for harvesting electrons from water oxidation by immobilization of PSII on electrode surfaces. Herein, the kinetics of electron transfer from QA- to [Co(III)(terpy)2]3+ (terpy = 2,2′;6′,2″-terpyridine) are investigated with a spectrophotometric assay revealing that the reaction follows Michaelis-Menten saturation kinetics, is inhibited by cations, and is not affected by variation of the QA reduction potential. A negatively charged site on the stromal surface of the PSII protein complex, composed of glutamic acid residues near QA, is hypothesized to bind cations, especially divalent cations. The cations are proposed to tune the redox properties of QA through electrostatic interactions. These observations may thus explain the molecular basis of the effect of divalent cations like Ca2+, Sr2+, Mg2+, and Zn2+ on the redox properties of the quinones in PSII, which has previously been attributed to long-range conformational changes propagated from divalent cations binding to the Ca(II)-binding site in the oxygen-evolving complex on the lumenal side of the PSII complex.

Original languageEnglish
Pages (from-to)7722-7728
Number of pages7
JournalJournal of Physical Chemistry B
Volume119
Issue number24
DOIs
Publication statusPublished - Jun 18 2015

Fingerprint

Photosystem II Protein Complex
Cations
Positive ions
cations
Electrons
Divalent Cations
quinones
electron transfer
electrons
Quinones
glutamic acid
Kinetics
Water
kinetics
Binding sites
Coulomb interactions
immobilization
water
Glutamic Acid
Assays

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Materials Chemistry
  • Surfaces, Coatings and Films

Cite this

Cation Effects on the Electron-Acceptor Side of Photosystem II. / Khan, Sahr; Sun, Jennifer S.; Brudvig, Gary W.

In: Journal of Physical Chemistry B, Vol. 119, No. 24, 18.06.2015, p. 7722-7728.

Research output: Contribution to journalArticle

Khan, Sahr ; Sun, Jennifer S. ; Brudvig, Gary W. / Cation Effects on the Electron-Acceptor Side of Photosystem II. In: Journal of Physical Chemistry B. 2015 ; Vol. 119, No. 24. pp. 7722-7728.
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