The role of D1-Ala344 in charge stabilization and recombination in Photosystem II

Krisztián Cser, Bruce A. Diner, Peter J. Nixon, I. Vass

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The Ala344 residue of the D1 protein has been identified as a crucial residue of the catalytic cluster of the water-oxidizing complex, however, its function has not been fully clarified. Here we have used thermoluminescence and flash-induced chlorophyll fluorescence measurements to characterize the effect of the D1-Ala344stop mutation on the electron transport of Photosystem II in intact cells of the cyanobacterium Synechocystis 6803. Although the mutant cannot grow photoautotrophically it shows flash-induced thermoluminescence and chlorophyll fluorescence signals reflecting the stabilization of negative and positive charges on the QA and QB quinone electron acceptors, and stable Photosystem II donors, respectively. Decay of flash induced chlorophyll fluorescence yield is multiphasic in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), with 6 ms, 350 ms, and 26 s time constants. When cells are illuminated with repetitive flashes, fired at 1 ms intervals, the 6 ms phase is gradually decreased with the concomitant increase of the 350 ms phase. After 45 min dark adaptation of mutant cells the 6 ms and 350 ms phases were significantly decreased and a very slow decaying component was formed. Flash induced oscillation of the thermoluminescence B band, which reflects the redox cycling of the water-oxidizing complex in the wild-type cells, was completely abolished in the D1-Ala344stop mutant. The results demonstrate that low efficiency photooxidation of Mn occurs in about 60% of the PSII centers. The photooxidizable Mn is unstable in the dark, and formation of higher S states is inhibited. In addition, the QA to QB electron transfer step is slowed down as an indirect consequence of the donor side modification. Our data indicate that the stabilization of a Mn ion by the α-carboxylate chain of the D1-Ala344 residue might represent one of the final steps in the assembly of functional catalytic sites for water oxidation.

Original languageEnglish
Pages (from-to)1049-1054
Number of pages6
JournalPhotochemical and Photobiological Sciences
Volume4
Issue number12
DOIs
Publication statusPublished - Dec 2005

Fingerprint

Thermoluminescence
Photosystem II Protein Complex
Chlorophyll
Diuron
Genetic Recombination
flash
Stabilization
stabilization
Fluorescence
chlorophylls
thermoluminescence
Water
cells
Photooxidation
Electrons
fluorescence
dark adaptation
Dark Adaptation
Synechocystis
water

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Cell Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Biophysics

Cite this

The role of D1-Ala344 in charge stabilization and recombination in Photosystem II. / Cser, Krisztián; Diner, Bruce A.; Nixon, Peter J.; Vass, I.

In: Photochemical and Photobiological Sciences, Vol. 4, No. 12, 12.2005, p. 1049-1054.

Research output: Contribution to journalArticle

Cser, Krisztián ; Diner, Bruce A. ; Nixon, Peter J. ; Vass, I. / The role of D1-Ala344 in charge stabilization and recombination in Photosystem II. In: Photochemical and Photobiological Sciences. 2005 ; Vol. 4, No. 12. pp. 1049-1054.
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abstract = "The Ala344 residue of the D1 protein has been identified as a crucial residue of the catalytic cluster of the water-oxidizing complex, however, its function has not been fully clarified. Here we have used thermoluminescence and flash-induced chlorophyll fluorescence measurements to characterize the effect of the D1-Ala344stop mutation on the electron transport of Photosystem II in intact cells of the cyanobacterium Synechocystis 6803. Although the mutant cannot grow photoautotrophically it shows flash-induced thermoluminescence and chlorophyll fluorescence signals reflecting the stabilization of negative and positive charges on the QA and QB quinone electron acceptors, and stable Photosystem II donors, respectively. Decay of flash induced chlorophyll fluorescence yield is multiphasic in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), with 6 ms, 350 ms, and 26 s time constants. When cells are illuminated with repetitive flashes, fired at 1 ms intervals, the 6 ms phase is gradually decreased with the concomitant increase of the 350 ms phase. After 45 min dark adaptation of mutant cells the 6 ms and 350 ms phases were significantly decreased and a very slow decaying component was formed. Flash induced oscillation of the thermoluminescence B band, which reflects the redox cycling of the water-oxidizing complex in the wild-type cells, was completely abolished in the D1-Ala344stop mutant. The results demonstrate that low efficiency photooxidation of Mn occurs in about 60{\%} of the PSII centers. The photooxidizable Mn is unstable in the dark, and formation of higher S states is inhibited. In addition, the QA to QB electron transfer step is slowed down as an indirect consequence of the donor side modification. Our data indicate that the stabilization of a Mn ion by the α-carboxylate chain of the D1-Ala344 residue might represent one of the final steps in the assembly of functional catalytic sites for water oxidation.",
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