Reduction of exogenous quinones and 2,6-dichlorophenol indophenol in cytochrome b-deficient yeast mitochondria: a differential effect on center i and center o of the cytochrome b-c1 complex.
The reduction of duroquinone (DQ), 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone (DB), and dichlorophenol indophenol (DCIP) by succinate and NADH was investigated in yeast mitochondria which have no spectrally detectable cytochrome b. Succinate reduces DB in the cytochrome b-deficient mitochondria at rates comparable to that observed in wild-type mitochondria, suggesting that succinate:ubiquinone oxidoreductase is unaffected by the lack of cytochrome b. In the mutant mitochondria, succinate does not reduce DQ or DCIP at significant rates; however, NADH reduces both DQ and DCIP at rates similar to that of the wild-type mitochondria in a myxothiazol, but not antimycin, sensitive reaction. The Ki for myxothiazol in this reaction is close to that for electron transfer through the cytochrome b-c1 complex. In addition, myxothiazol does not inhibit NADH:ubiquinone oxidoreductase. These results confirm our previous suggestion that the cytochrome b-c1 complex is involved in electron transfer from the primary dehydrogenases to DQ and DCIP and suggest that cytochrome b is not the binding site for myxothiazol.
Zhu
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Department of Biochemistry, West Virginia University School of Medicine, Morgantown 26506.
Sprague
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Beattie
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D015086:2,6-Dichloroindophenol / Q000378:metabolism*; D000968:Antimycin A / Q000031:analogs & derivatives / Q000494:pharmacology; D001665:Binding Sites; D002734:Chlorophyll / Q000378:metabolism*; D003573:Cytochrome b Group / Q000172:deficiency*; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000378:metabolism*; D007215:Indophenol / Q000031:analogs & derivatives*; D045342:Light-Harvesting Protein Complexes; D008689:Methacrylates; D008928:Mitochondria / Q000378:metabolism; D009154:Mutation; D009243:NAD / Q000494:pharmacology; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins / Q000378:metabolism*; D011809:Quinones / Q000378:metabolism*; D013386:Succinates / Q000494:pharmacology; D019802:Succinic Acid; D013844:Thiazoles / Q000494:pharmacology; D015003:Yeasts / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
D003573:Cytochrome b Group; D045342:Light-Harvesting Protein Complexes; D008689:Methacrylates; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins; D011809:Quinones; D013386:Succinates; D013844:Thiazoles; D009243:NAD; C032456:antimycin; D002734:Chlorophyll; D007215:Indophenol; D000968:Antimycin A; C030517:myxothiazol; D019802:Succinic Acid; D015086:2,6-Dichloroindophenol; D014450:Electron Transport Complex III