title: Modification of the spectral properties of cytochrome b in mutants of Saccharomyces cerevisiae resistant to 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Mapping at two distinct genetic loci of the split mitochondrial gene of cytochrome b.
abstract: The effects of five inhibitors of the cytochrome bc1 complex: 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), 2-n-heptyl-4-hydroxyquinoline-N-oxide (HpHOQnO), antimycin A, funiculosin and mucidin were measured in submitochondrial particles of strains of the yeast Saccharomyces cerevisiae belonging to two classes of diuron-resistant mutants Diu 1 and Diu 2 which are modified in different exons of the split mitochondrial gene of cytochrome b. 1. The oxidation of NADH and of cytochrome b-561 exhibits a similar resistance to diuron and HpHOQnO in Diu 1 and Diu 2 mutants. 2. No extra reduction of cytochrome b-561 and cytochrome b-565 is observed in the presence of diuron and HpHOQnO. 3. Both Diu 1 and Diu 2 mutants exhibit the red shift of cytochrome b-561 induced by concentrations of HpHOQno 2 -- 3-times higher than those required in the parental strains. 4. The spectral and respiratory effects of antimycin A, funiculosin and mucidin and generally similar in the diuron-resistant mutants and in their parental strains. However a cross-resistance between diuron and antimycin A is indicated in one Diu 2 mutant. 5. From the combined genetic and biochemical data it is concluded that the interaction of diuron and HpHOQnO with cytochrome b is mediated by at least two specific amino acids located apart in the central region of the apocytochrome b peptide coded by mitochondrial DNA. These two amino acids control tightly the extra reduction of cytochromes b-565 and b-561 as well as the flow of electrons through the bc1 complex. However the binding of HpHOQnO required for the expression of the red shift of cytochrome b-561 is only slightly affected by the diu-1 and diu-2 mutations.
mesh_terms: D000968:Antimycin A / Q000494:pharmacology; D003573:Cytochrome b Group; D003574:Cytochrome c Group / Q000037:antagonists & inhibitors; D003580:Cytochromes / Q000235:genetics* / Q000378:metabolism; D004237:Diuron / Q000494:pharmacology*; D014450:Electron Transport Complex III; D008928:Mitochondria / Q000032:analysis*; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects; D011808:Quinone Reductases / Q000037:antagonists & inhibitors; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D013053:Spectrophotometry; D013367:Submitochondrial Particles / Q000032:analysis
chemical_list: D003573:Cytochrome b Group; D003574:Cytochrome c Group; D003580:Cytochromes; D009097:Multienzyme Complexes; C023646:cytochrome b561; D000968:Antimycin A; D004237:Diuron; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D011808:Quinone Reductases; D014450:Electron Transport Complex III