Yeast cytochrome c oxidase subunit VII is essential for assembly of an active enzyme. Cloning, sequencing, and characterization of the nuclear-encoded gene

Abstract

The gene COX VII coding for yeast cytochrome c oxidase subunit VII has been cloned by a two-step procedure. Two degenerate oligonucleotides corresponding to amino- and carboxyl-terminal protein segments were used in a polymerase chain reaction for the amplification of a major portion of subunit VII (residues 1-52), which was then used for the cloning of complete COX VII. From the nucleotide sequence, an additional amino-terminal and two additional carboxyl-terminal amino acids are predicted as compared with the described primary sequence (Power, S. D., Lochrie, M. A., and Poyton, R. O. (1986) J. Biol. Chem. 261, 9206-9209). Beside subunit VIIa the subunit described here is the only nuclear encoded subunit of cytochrome c oxidase in yeast without a leader sequence. COX VII exists as a single copy per haploid genome as shown by Southern blot and gene disruption. Null mutants produced by gene disruption at the COX VII locus were respiratory-deficient. No cytochrome c oxidase activity was detectable nor was there an assembly of the oxidase complex.