Influence of the redox potential of the primary quinone electron acceptor on photoinhibition in photosystem II

Christian Fufezan*, Christine M. Gross, Martin Sjödin, A. William Rutherford, Anja Krieger-Liszkay, Diana Kirilovsky

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

73 Citations (Scopus)


We report the characterization of the effects of the A249S mutation located within the binding pocket of the primary quinone electron acceptor, Q A, in the D2 subunit of photosystem II in Thermosynechococcus elongatus. This mutation shifts the redox potential of QA by ∼-60 mV. This mutant provides an opportunity to test the hypothesis, proposed earlier from herbicide-induced redox effects, that photoinhibition (light-induced damage of the photosynthetic apparatus) is modulated by the potential of QA. Thus the influence of the redox potential of Q A on photoinhibition was investigated in vivo and in vitro. Compared with the wild-type, the A249S mutant showed an accelerated photoinhibition and an increase in singlet oxygen production. Measurements of thermoluminescence and of the fluorescence yield decay kinetics indicated that the charge-separated state involving QA was destabilized in the A249S mutant. These findings support the hypothesis that a decrease in the redox potential of Q A causes an increase in singlet oxygen-mediated photoinhibition by favoring the back-reaction route that involves formation of the reaction center chlorophyll triplet. The kinetics of charge recombination are interpreted in terms of a dynamic structural heterogeneity in photosystem II that results in high and low potential forms of QA. The effect of the A249S mutation seems to reflect a shift in the structural equilibrium favoring the low potential form.

Original languageEnglish
Pages (from-to)12492-12502
Number of pages11
JournalJournal of Biological Chemistry
Issue number17
Publication statusPublished - 2007 Apr 27
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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