The Photo-Oxidation of Low-Potential Hemes in the Tetraheme Cytochrome Subunit of the Reaction Center in Whole Cells of Blastochloris viridis

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The reduction and the photo-oxidation of the lowpotential hemes in the tetraheme cytochrome subunit of the photosynthetic reaction center complex (RC) of the purple non-sulfur bacterium Blastochloris (Rhodopseudomonas) viridis was observed in whole cells after long incubation in the dark. The low-potential hemes showed fast photo-oxidation, similar to the high-potential hemes, as the common feature of the hemes in the RC-bound tetraheme cytochrome; while their re-reduction was very slow, compared to those of the high-potential hemes. Myxothiazol, a specific inhibitor of the cytochrome bc_1 complex, had only minor effect on the re-reduction of low-potential hemes, suggesting that low-potential hemes are not efficiently re-reduced by the electrons from the cytochrome bc_1 complex and ubiquinones. These results showed the participation of low-potential hemes in photosynthetic electron transfer in vivo. The physiological function of the low-potential hemes in vivo is discussed.
日本植物生理学会の論文