The cytochrome bc1 and cytochrome c oxidase complexes associate to form a single supracomplex in yeast mitochondria

Abstract

The mitochondrial electron transport chain complexes are large multisubunit complexes embedded in the inner membrane. We report here that in the yeast Saccharomyces cerevisiae, the cytochrome bc1 and cytochrome c oxidase complexes co-exist as a larger complex of ~1000 kDa in the mitochondrial membrane. Following solubilization with a mild detergent, the cytochrome bc1-cytochrome c oxidase complex remains stable. It was analyzed using the techniques of gel filtration and blue native-polyacrylamide gel electrophoresis. Direct physical association of subunits of the cytochrome bc1 complex with those of the cytochrome c oxidase complex was verified by co-immunoprecipitation analysis. Our data indicate that the cytochrome bc1 complex is exclusively in association with the cytochrome c oxidase complex in yeast mitochondria. We term this complex the cytochrome bc1-cytochrome c oxidase supracomplex.