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 language | English |
|---|---|
| Pages (from-to) | 7722-7728 |
| Number of pages | 7 |
| Journal | Journal of Physical Chemistry B |
| Volume | 119 |
| Issue number | 24 |
| DOIs | |
| Publication status | Published - Jun 18 2015 |
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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 journal › Article
}
TY - JOUR
T1 - Cation Effects on the Electron-Acceptor Side of Photosystem II
AU - Khan, Sahr
AU - Sun, Jennifer S.
AU - Brudvig, Gary W
PY - 2015/6/18
Y1 - 2015/6/18
N2 - 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.
AB - 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.
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U2 - 10.1021/jp513035u
DO - 10.1021/jp513035u
M3 - Article
VL - 119
SP - 7722
EP - 7728
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
SN - 1520-6106
IS - 24
ER -