Biogenesis of the yeast cytochrome bc1 complex

The mitochondrial respiratory chain is composed of four different protein complexes that cooperate in electron transfer and proton pumping across the inner mitochondrial membrane. The cytochrome bc(1) complex, or complex III, is a component of the mitochondrial respiratory chain. This review will focus on the biogenesis of the bc(1) complex in the mitochondria of the yeast Saccharomyces cerevisiae. In wild type yeast mitochondrial membranes the major part of the cytochrome bc(1) complex was found in association with one or two copies of the cytochrome c oxidase complex. The analysis of several yeast mutant strains in which single genes or pairs of genes encoding bc(1) subunits had been deleted revealed the presence of a common set of bc(1) sub-complexes. These sub-complexes are represented by the central core of the bc(1) complex, consisting of cytochrome b bound to subunit 7 and subunit 8, by the two core proteins associated with each other, by the Rieske protein associated with subunit 9, and by those deriving from the unexpected interaction of each of the two core proteins with cytochrome c(1). Furthermore, a higher molecular mass sub-complex is that composed of cytochrome b, cytochrome c(1), core protein 1 and 2, subunit 6, subunit 7 and subunit 8. The identification and characterization of all these sub-complexes may help in defining the steps and the molecular events leading to bc(1) assembly in yeast mitochondria. (C) 2008 Elsevier B.V. All rights reserved.