Replacement of a Conserved Glycine Residue in Subunit II of Cytochrome C Oxidase Interferes with Protein Function

In this paper we describe the isolation and characterization of a respiration-deficient yeast strain which is defective in the function of subunit II of cytochrome c oxidase. This strain, VC32, carries a mutation in the mitochondrial COX2 gene which converts a conserved glycine residue to arginine. The conserved glycine is in a region implicated as important for ligating the CuA redox center and for interaction with cytochrome c. We have also characterized five revertants of VC32 which have recovered respiratory function; all five were mapped to the mitochondrial genome. In three of the five revertants the wild-type glycine codon is restored, while in two of the five the mutant arginine codon is still present. These two strains are likely to possess alterations either in components of the mitochondrial translation machinery or in mitochondrially-encoded gene products that interact directly with subunit II to assemble an active oxidase complex.