Mitochondrial membrane biogenesis: characterization and use of pet mutants to clone the nuclear gene coding for subunit V of yeast cytochrome c oxidase.
A nuclear pet mutant of Saccharomyces cerevisiae that is defective in the structural gene for subunit V of cytochrome c oxidase has been identified and used to clone the subunit V gene (COX5) by complementation. This mutant, E4-238 [24], and its revertant, JM110, produce variant forms of subunit V. In comparison to the wild-type polypeptide (Mr = 12,500), the polypeptides from E4-238 and JM110 have apparent molecular weights of 9,500 and 13,500, respectively. These mutations directly alter the subunit V structural gene rather than a gene required for posttranslational processing or modification of subunit V because they are cis-acting in diploid cells; that is, both parental forms of subunit V are produced in heteroallelic diploids formed from crosses between the mutant, revertant, and wild type. Several plasmids containing the COX5 gene were isolated by transformation of JM28, a derivative of E4-238, with DNA from a yeast nuclear DNA library in the vector YEp13. One plasmid, YEp13-511, with a DNA insert of 4.8 kilobases, was characterized in detail. It restores respiratory competency and cytochrome oxidase activity in JM28, encodes a new form of subunit V that is functionally assembled into mitochondria, and is capable of selecting mRNA for subunit V. The availability of mutants altered in the structural gene for subunit V (COX5) and of the COX5 gene on a plasmid, together with the demonstration that plasmid-encoded subunit V is able to assemble into a functional holocytochrome c oxidase, enables molecular genetic studies of subunit V assembly into mitochondria and holocytochrome c oxidase.
D003001:Cloning, Molecular; D003576:Electron Transport Complex IV / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics*; D005796:Genes; D005800:Genes, Fungal; D007425:Intracellular Membranes / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000235:genetics*
D005656:Fungal Proteins; D008565:Membrane Proteins; D003576:Electron Transport Complex IV