Partial assembly of the yeast mitochondrial ATP synthase

The mitochondrial ATP synthase is a molecular motor that drives the phospho rylation of ADP to ATP. The yeast mitochondrial ATP synthase is composed of at least 19 different peptides, which comprise the F-1 catalytic domain, t he F-o proton pore, and two stalks, one of which is thought to act as a sta tor to link and hold F-1 to F-o, and the other as a rotor. Genetic studies using yeast Saccharomyces cerevisiae have suggested the hypothesis that the yeast mitochondrial ATP synthase can be assembled in the absence of 1, and even 2, of the polypeptides that are thought to comprise the rotor. Howeve r, the enzyme complex assembled in the absence of the rotor is thought to b e uncoupled, allowing protons to freely flow through Fo into the mitochondr ial matrix. Left uncontrolled, this is a lethal process and the cell must e liminate this leak if it is to survive. In yeast, the cell is thought to lo se or delete its mitochondrial DNA (the petite mutation) thereby eliminatin g the genes encoding essential components of F-o. Recent biochemical studie s in yeast, and prior studies in E. coli, have provided support for the ass embly of a partial ATP synthase in which the ATP synthase is no longer coup led to proton translocation.