The function of D1-H332 in Photosystem II electron transport studied by thermoluminescence and chlorophyll fluorescence in site-directed mutants of Synechocystis 6803

Yagut Allahverdiyeva, Zsuzsanna Deák, András Szilárd, Bruce A. Diner, Peter J. Nixon, Imre Vass

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The His332 residue of the D1 protein has been identified as the likely ligand of the catalytic Mn ions in the water oxidizing complex (Ferreira, K.N., Iverson, T.M., Maghlaoui, K., Barber, J. & Iwata, S. (2004) Science 303, 1831-1838). However, its function has not been fully clarified. Here we used thermoluminescence and flash-induced chlorophyll fluorescence measurements to characterize the effect of the D1-H333E, D1-H332D and D1-H332S mutations on the electron transport of Photosystem II in intact cells of the cyanobacterium Synechocystis 6803. Although the mutants are not photoautotrophic they all show flash-induced thermoluminescence and chlorophyll fluorescence, which originate from the S2QA- and S2Q B- recombinations demonstrating that charge stabilization takes place in the water oxidizing complex. However, the conversion of S 2 to higher S states is inhibited and the energetic stability of the S2QA- charge pair is increased by 75, 50 and 7 mV in the D1-H332D, D1-H332E and D1-H332S mutants, respectively. This is most probably caused by a decrease of Em(S2/S1). Concomitantly, the rate of electron donation from Mn to Tyr-Z. during the S1 to S2 transition is slowed down, relative to the wild type, 350- and 60-fold in the D1-H332E and D1-H332D mutants, respectively, but remains essentially unaffected in D1-H332S. A further effect of the D1-H332E and D1-H332D mutations is the retardation of the QA to QB electron transfer step as an indirect consequence of the donor side modification. Our data show that although the His residue in the D1-332 position can be substituted by other metal binding residues for binding photo-oxidisable Mn it is required for controlling the functional redox energetics of the Mn cluster.

Original languageEnglish
Pages (from-to)3523-3532
Number of pages10
JournalEuropean Journal of Biochemistry
Issue number17
Publication statusPublished - Sep 1 2004



  • D1-protein
  • Flash-induced chlorophyll fluorescence
  • His332 mutants
  • Photosystem II
  • Thermoluminescence

ASJC Scopus subject areas

  • Biochemistry

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