title: Reduction of cytochromes b6 and f in isolated plastoquinol-plastocyanin oxidoreductase driven by photochemical reaction centers from Rhodopseudomonas sphaeroides.
abstract: Photochemical reaction centers isolated from the bacterium Rhodopseudomonas sphaeroides are able to donate electrons to cytochromes b6 and f in the plastoquinol,-platocyanin oxidoreductase isolated from spinach chloroplasts. The reduction reactions occur only after the second single turnover flash, in a reaction which is sensitive to inhibitors of the reactions in the chloroplast membranes. When all the components of the b6f complex are oxidized prior to activation, both cytochromes b6 and f are reduced after the second flash. If cytochrome f is reduced prior to activation, cytochrome b6 is still reduced after the second flash, but as the potential is lowered so that the Rieske iron-sulfur cluster is reduced prior to activation, the reduction of cytochrome b6 fails. The b6f complex thus functions in such a way that a two-electron redox couple, probably a quinone, is capable of reducing both cytochrome b6 and cytochrome f, the latter via the Rieske iron-sulfur cluster, in a coupled reaction where both electrons must leave the two-electron carrier. Cytochrome b6 is thus reduced in a manner analogous to "oxidant-induced reduction."
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D003580:Cytochromes / Q000378:metabolism*; D045348:Cytochromes f; D007700:Kinetics; D008027:Light; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D045322:Photosynthetic Reaction Center Complex Proteins; D012242:Rhodobacter sphaeroides / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D003580:Cytochromes; D045322:Photosynthetic Reaction Center Complex Proteins; D045348:Cytochromes f; D010088:Oxidoreductases