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 resp iration-deficient yeast strain which is defective in the function of s ubunit II of cytochrome c oxidase. This strain, VC32, carries a mutati on in the mitochondrial COX2 gene which converts a conserved glycine r esidue to arginine. The conserved glycine is in a region implicated as important for ligating the Cu, 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 mito chondrial genome. In three of the five revertants the wild-type glycin e codon is restored, while in two of the five the mutant arginine codo n is still present. These two strains are likely to possess alteration s either in components of the mitochondrial translation machinery or i n mitochondrially-encoded gene products that interact directly with su bunit II to assemble an active oxidase complex.