title: Antimycin inhibition of the cytochrome bd complex from Azotobacter vinelandii indicates the presence of a branched electron transfer pathway for the oxidation of ubiquinol.
abstract: Antimycin A and UHBDT inhibit the activity of the purified cytochrome bd complex from Azotobacter vinelandii. Inhibition of activity is non-competitive and antimycin A binding induces a shift to the red in the spectrum of a b-type haem. No inhibitory effects were seen with myxothiazol. Steady-state experiments indicate that the site of inhibition for antimycin A lies on the low-potential side of haem b558. In the presence of antimycin A at concentrations sufficient to inhibit respiration, some direct electron transfer from ubiquinol-1 to haem b595 and haem d still occurs. The results are consistent with a branched electron transfer pathway from ubiquinol to the oxygen reduction site.
authors.affiliation: Metals in Biology and Medicine Centre, King's College London, UK.
authors.forename: S
authors.initials: S
authors.lastname: Jünemann
authors.forename: J M
authors.initials: JM
authors.lastname: Wrigglesworth
mesh_terms: D000968:Antimycin A / Q000494:pharmacology*; D016948:Azotobacter vinelandii / Q000201:enzymology*; D003573:Cytochrome b Group; D003580:Cytochromes / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D004579:Electron Transport; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D007700:Kinetics; D008689:Methacrylates; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D013844:Thiazoles / Q000494:pharmacology; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: C025993:5-n-undecyl-6-hydroxy-4,7-dioxobenzothiazole; D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D008689:Methacrylates; D013844:Thiazoles; D014451:Ubiquinone; D000968:Antimycin A; C030517:myxothiazol; D010088:Oxidoreductases; C040077:cytochrome bd terminal oxidase complex, E coli; C003741:ubiquinol; D004229:Dithiothreitol