RESUMO
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 bc(1) and cytochrome c oxidase complexes co-exist as a larger complex of approximately 1000 kDa in the mitochondrial membrane. Following solubilization with a mild detergent, the cytochrome bc(1)-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 bc(1) complex with those of the cytochrome c oxidase complex was verified by co-immunoprecipitation analysis. Our data indicate that the cytochrome bc(1) complex is exclusively in association with the cytochrome c oxidase complex in yeast mitochondria. We term this complex the cytochrome bc(1)-cytochrome c oxidase supracomplex.
Assuntos
Complexo III da Cadeia de Transporte de Elétrons/metabolismo , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Mitocôndrias/enzimologia , Transporte de Elétrons , Eletroforese em Gel de Poliacrilamida , Membranas Intracelulares/enzimologia , Substâncias Macromoleculares , Peso Molecular , Conformação Proteica , LevedurasRESUMO
Bcs1p, a mitochondrial protein and member of the conserved AAA protein family, is involved in the biogenesis of the cytochrome bc(1) complex. We demonstrate here that Bcs1p is directly required for the assembly of the Rieske FeS and Qcr10p proteins into the cytochrome bc(1) complex. Bcs1p binds to a precomplex in the assembly pathway of the cytochrome bc(1) complex. Binding of Bcs1p to and release from this assembly intermediate is driven by ATP hydrolysis. We propose that Bcs1p acts as an ATP-dependent chaperone, maintaining the precomplex in a competent state for the subsequent assembly of the Rieske FeS and Qcr10p proteins.
