Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
Volume 1787, Issue 3, Pages 191-200Publisher
ELSEVIER
DOI: 10.1016/j.bbabio.2008.12.014
Keywords
Divinyl chlorophyll; Photosystem II; Delayed fluorescence; Cyanobacteria; Synechocystis sp PCC 6803
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Funding
- Japanese Society for the Promotion of Science (JSPS) [17GS0314]
- Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT) [19614007, 18350067]
- Grants-in-Aid for Scientific Research [18350067, 19614007] Funding Source: KAKEN
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Chlorophyll (Chl) a in a cyanobacterium Synechocystis sp. PCC 6803 was replaced with di-vinyl (DV)-Chl a by knock-out of the specific gene (slr1923), responsible for the reduction of a 8-vinyl group, and optical and photochemical properties of purified photosystem (PS) II complexes DV-PS II) were investigated. We observed differences in the peak wavelengths of absorption and fluorescence spectra; however, replacement of Chl a with DV-Chl a had limited effects. On the contrary, photochemical reactions were highly sensitive to high-light treatments in the mutant. Specifically, DV-Chl a was rapidly bleached under high-light conditions, and we detected significant dissociation of complexes and degradation of D1 proteins (PsbA). By comparing the SDS-PAGE patterns observed in this study to those observed in spinach chloroplasts, this degradation is assigned to the acceptor-side photoinhibition. The delayed fluorescence in the nanosecond time region at 77 K was suppressed in DV-PS II, possibly increasing triplet formation of Chl molecules. Our findings provide insight into the evolutionary processes of cyanobacteria. The effects of pigment replacement on the optimization of reactions are discussed. (C) 2009 Elsevier B.V. All rights reserved.
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