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 language | English |
|---|---|
| Pages (from-to) | 1049-1054 |
| Number of pages | 6 |
| Journal | Photochemical and Photobiological Sciences |
| Volume | 4 |
| Issue number | 12 |
| DOIs | |
| Publication status | Published - Dec 2005 |
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ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Cell Biology
- Biochemistry, Genetics and Molecular Biology(all)
- Biochemistry
- Biophysics
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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 journal › Article
}
TY - JOUR
T1 - The role of D1-Ala344 in charge stabilization and recombination in Photosystem II
AU - Cser, Krisztián
AU - Diner, Bruce A.
AU - Nixon, Peter J.
AU - Vass, I.
PY - 2005/12
Y1 - 2005/12
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=29244491995&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=29244491995&partnerID=8YFLogxK
U2 - 10.1039/b512354m
DO - 10.1039/b512354m
M3 - Article
C2 - 16307121
AN - SCOPUS:29244491995
VL - 4
SP - 1049
EP - 1054
JO - Photochemical and Photobiological Sciences
JF - Photochemical and Photobiological Sciences
SN - 1474-905X
IS - 12
ER -