title: The Rhodospirillum rubrum cytochrome bc1 complex: peptide composition, prosthetic group content and quinone binding.
abstract: A cytochrome bc1 complex, essentially free of bacteriochlorophyll, has been purified from the photosynthetic purple non-sulfur bacterium Rhodospirillum rubrum. The complex catalyzes electron flow from quinol to cytochrome c (turnover number = 75 s-1) that is inhibited by low concentrations of antimycin A and myxothiazol. The complex contains only three peptide subunits: cytochrome b (Mr = 35,000); cytochrome c1 (Mr = 31,000) and the Rieske iron-sulfur protein (Mr = 22,400). Em values (pH 7.4) were measured for cytochrome c1 (+320 mV) and the two hemes of cytochrome b (-33 and -90 mV). Electron flow from quinol to cytochrome c is inhibited when the complex is pre-illuminated in the presence of a ubiquinone photoaffinity analog (azido-Q). During illumination, the azido-Q becomes covalently attached to the cytochrome b peptide and, to a lesser extent, to cytochrome c1.
authors.affiliation: Department of Chemistry and Biochemistry, Texas Tech University, Lubbock 79409.
authors.forename: A
authors.initials: A
authors.lastname: Kriauciunas
authors.forename: L
authors.initials: L
authors.lastname: Yu
authors.forename: C A
authors.initials: CA
authors.lastname: Yu
authors.forename: R M
authors.initials: RM
authors.lastname: Wynn
authors.forename: D B
authors.initials: DB
authors.lastname: Knaff
mesh_terms: D000345:Affinity Labels; D001386:Azides; D016227:Benzoquinones; D003573:Cytochrome b Group / Q000032:analysis; D003574:Cytochrome c Group / Q000032:analysis / Q000378:metabolism; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007506:Iron-Sulfur Proteins / Q000032:analysis; D008970:Molecular Weight; D010455:Peptides / Q000032:analysis*; D010777:Photochemistry; D011809:Quinones / Q000378:metabolism*; D012247:Rhodospirillum rubrum / Q000201:enzymology*; D013053:Spectrophotometry; D014451:Ubiquinone / Q000031:analogs & derivatives
chemical_list: D000345:Affinity Labels; D001386:Azides; D016227:Benzoquinones; D003573:Cytochrome b Group; D003574:Cytochrome c Group; D007506:Iron-Sulfur Proteins; D010455:Peptides; D011809:Quinones; C037989:Rieske iron-sulfur protein; D014451:Ubiquinone; C004532:quinone; C048123:3-azido-2-methyl-5-methoxy-6-(3,7-dimethyloctyl)-1,4-benzoquinone; D014450:Electron Transport Complex III