Diminished degradation of yeast cytochrome c by interactions with its physiological partners.
The level and structure of yeast iso-1-cytochrome c and iso-2-cytochrome c, encoded by the nuclear genes CYC1 and CYC7, respectively, are normally not altered in rho- mutants, which completely lack the cytochromes a.a3 subunits and cytochrome b that are encoded by mitochondrial DNA. In contrast, iso-cytochromes c containing the amino acid change Thr-78-->Ile (T78I) were observed at the normal or near-normal wild-type level in rho+ strains but were completely absent in rho- mutants. We have demonstrated with the "global" suppressor mutation Asn-52-->Ile and by pulse-chase labeling that the T78I iso-1-cytochrome c undergoes rapid cellular degradation in rho- mutants. Furthermore, specific mutations revealed that the deficiency of T78I iso-1 cytochrome c can be caused by the lack of cytochrome a.a3 or cytochrome c1, but not by the lack of cytochrome b. Thus, this and certain other, but not all, labile forms of cytochrome c are protected from degradation by the interaction with its physiological partners.
Pearce
D A
DA
Department of Biochemistry, University of Rochester School of Medicine and Dentistry, NY 14642, USA.
Sherman
F
F
D000483:Alleles; D001483:Base Sequence; D003574:Cytochrome c Group / Q000235:genetics / Q000378:metabolism*; D045304:Cytochromes c; D003575:Cytochromes c1 / Q000235:genetics / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D005838:Genotype; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D013053:Spectrophotometry
C014059:CYC1 protein, S cerevisiae; D003574:Cytochrome c Group; D009838:Oligodeoxyribonucleotides; D029701:Saccharomyces cerevisiae Proteins; C032139:iso-2-cytochrome C; D045304:Cytochromes c; D003575:Cytochromes c1; D003576:Electron Transport Complex IV