Partial Assembly of the Yeast Mitochondrial ATP Synthase 1

The mitochondrial ATP synthase is a molecular motor that drives the phosphorylation ofADP to ATP. The yeast mitochondrial ATP synthase is composed of at least 19 differentpeptides, which comprise the F₁ catalytic domain, the F₀ proton pore, and two stalks, oneof which is thought to act as a stator to link and hold F₁ to F₀, and the other as a rotor.Genetic studies using yeast Saccharomyces cerevisiae have suggested the hypothesis thatthe yeast mitochondrial ATP synthase can be assembled in the absence of 1, and even 2, ofthe polypeptides that are thought to comprise the rotor. However, the enzyme complexassembled in the absence of the rotor is thought to be uncoupled, allowing protons to freelyflow through F₀ into the mitochondrial matrix. Left uncontrolled, this is a lethal process andthe cell must eliminate this leak if it is to survive. In yeast, the cell is thought to lose ordelete its mitochondrial DNA (the petite mutation) thereby eliminating the genes encodingessential components of F₀. Recent biochemical studies in yeast, and prior studies in E. coli,have provided support for the assembly of a partial ATP synthase in which the ATP synthaseis no longer coupled to proton translocation.