Disruption of the gene encoding subunit VI of yeast cytochrome bc₁ complex causes respiratory deficiency of cells with reduced cytochrome c levels

Abstract

A double mutant of Saccharomyces cerevisiae, in which CYCI gene is deleted and the chromosomal copy of the 17 kDa protein gene is disrupted, has been constructed. This mutant cannot grow on nonfermentable carbon sources, but normal growth can be restored by complementation of either mutation with a yeast vector containing either the wild-type 17 kDa protein gene or the CYCI gene. These results show that although the 17 kDa protein, subunit VI of yeast cytochrome bq complex is dispensable for yeast mitochondrial respiration in cells with the wild-type levels of cytochrome c, the 17 kDa protein is essential for respiration when the level of cytoehrome c is limited, indicating that is plays a role in electron transport. This glycerol-phenotype of the double mutant can serve as the basis for further genetic studies on the function of the 17 kDa protein in yeast mitochondria and may provide insight into the physiological function of the hinge protein, the counterpart of the yeast 17 kDa protein, in beef heart mitochondria.Yeast 17 kDa protein; Cytochrome bc 1 complex; Glycerol-mutant; Respiration

QSR1, an Essential Yeast Gene with a Genetic Relationship to a Subunit of the Mitochondrial Cytochrome bc1Complex, Is Homologous to a Gene Implicated in Eukaryotic Cell Differentiation

“…Si nce QCR 6 encodes a protein wh ose only kn own fun ct ion is in a resp ira tory enzyme com plex , we expecte d to find mu tan ts t hat req uired QCR 6 to grow on ly on non -fermentabl e ca rbon sou rces. For exa m ple, yeast st ra ins in which both QCR6 a nd CYC 1 are deleted a re pet ite , whil e st ra ins in whi ch eit he r ge ne a lone is deleted a re not (35). Simil arly, we ha ve obse rve d th at combi ned delet ions of QCR 6 a nd QCR 9 , th e ge ne for subu n it 9 of t he bc ; com plex, resu lt s in a sy nt het ic petite ph en otype."…”

A functional analysis of mitochondrial respiratory chain cytochrome bc1 complex in Gaeumannomyces tritici by RNA silencing as a possible target of carabrone

“…The mitochondrial respiratory chain cytochrome bc 1 complex (complex III, ubiquinol:cytochrome c oxidoreductase) is a central segment in the mitochondrial respiratory chain. Mitochondrial complex III catalyses electron transfer from ubihydroquinone to cytochrome c , accompanied by vectorial proton translocation across the membrane, thus generating ATP (Kim and Zitomer, 1990; Lange and Hunte, 2002). The mitochondrial cytochrome bc 1 complex isolated from beef heart is a dimer, with each monomer comprising 11 different polypeptide subunits, and the relative molecular mass of a monomer is 240 kDa (Iwata et al ., 1998).…”

The acidic domain of cytochrome c1 in Paracoccus denitrificans, analogous to the acidic subunits in eukaryotic bc1 complexes, is not involved in the electron transfer reaction to its native substrate cytochrome c552

“…In this stretch no basic residue is found, thus showing a high analogy to the acidic domain of Qcr6p from yeast or the hinge protein from bovine heart, suggesting a similar function. For the eukaryotic counterparts a role in cytochrome c interaction was proposed [9-16]. In addition these acidic domains of yeast and P. denitrificans complex III (on the Qcr6p and on the cytochrome c 1 , resp. )…”