Structure and function of Pet100p, a molecular chaperone required for the assembly of cytochrome c oxidase in Saccharomyces cerevisiae

The assembly of cytochrome c oxidase in the inner mitochondrial membranes o f eukaryotic cells requires the protein products of a large number of nucle ar genes. In yeast, some of these act globally and affect the assembly of s everal respiratory-chain protein complexes, whereas others act in a cytochr ome c oxidase-specific fashion. Many of these yeast proteins have human cou nterparts, which when mutated lead to energy-related diseases. One of these proteins, Pet100p, is a novel molecular chaperone that functions to incorp orate a subcomplex containing cytochrome c oxidase subunits VII, VIIa and V III into holo-(cytochrome c oxidase). Here we report the topological dispos ition of Pet100p in the inner mitochondrial membrane and show that its C-te rminal domain is essential for its function as a cvtochrome c oxidase-speci fic 'assembly facilitator'.