title: Light-activated proton-motive force generation in lipid vesicles containing cytochrome b-c1 complex and bacterial reaction centres.
abstract: (1) Purified bovine heart mitochondrial cytochrome b-c1 complex (ubiquinone-cytochrome c oxidoreductase) and photosynthetic reaction centres isolated from Rhodopseudomonas sphaeroides strain R-26 have been incorporated into lipid vesicles. In the presence of cytochrome c and ubiquinone-2, light activation caused a cyclic electron transfer involving both components. (2) Since cytochrome c is added outside the vesicles, it is both reduced by the cytochrome b-c1 complex and oxidised by the reaction centre on the outside of the vesicles. Ubiquinone-2, however, is reduced by the reaction centres at a site in contact with the inside of the vesicles, but the reduced form, ubiquinol-2, is oxidised by the cytochrome b-c1 complex at a site in contact with the outer aqueous phase. (3) In the presence of valinomycin plus K+, initiation of cyclic electron flow causes protons to move from inside the vesicles to the outer medium and the H +/2e- ratio was calculated to be close to 4.
mesh_terms: D000818:Animals; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002417:Cattle; D014450:Electron Transport Complex III; D007700:Kinetics; D008051:Lipid Bilayers / Q000378:metabolism; D008929:Mitochondria, Heart / Q000201:enzymology; D009097:Multienzyme Complexes / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010775:Photic Stimulation; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins / Q000378:metabolism*; D011522:Protons; D011808:Quinone Reductases / Q000378:metabolism*; D012242:Rhodobacter sphaeroides; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D008051:Lipid Bilayers; D009097:Multienzyme Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins; D011522:Protons; D014451:Ubiquinone; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D009247:NADH, NADPH Oxidoreductases; D011808:Quinone Reductases; D014450:Electron Transport Complex III; C003741:ubiquinol