The cytoplasmically-made subunit IV is necessary for assembly of cytochrome c oxidase in yeast

EMBO J. 1985 Jan;4(1):179-84.


Yeast cytochrome c oxidase contains three large subunits made in mitochondria and at least six smaller subunits made in the cytoplasm. There is evidence that the catalytic centers (heme a and copper) are associated with the mitochondrially-made subunits, but the role of the cytoplasmically-made subunits has remained open. Using a gene interruption technique, we have now constructed a Saccharomyces cerevisiae mutant which lacks the largest of the cytoplasmically-made subunits (subunit IV). This mutant is devoid of cyanide-sensitive respiration, the absorption spectrum of cytochrome aa3 and cytochrome c oxidase activity. It still contains the other cytochrome c oxidase subunits but these are not assembled into a stable complex. Active cytochrome c oxidase was restored to the mutant by introducing a plasmid-borne wild-type subunit IV gene; no restoration was seen with a gene carrying an internal deletion corresponding to amino acid residues 28-66 of the mature subunit. Subunit IV is thus necessary for proper assembly of cytochrome c oxidase.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cytoplasm / metabolism*
  • Electron Transport Complex IV / genetics*
  • Extrachromosomal Inheritance
  • Genes
  • Mutation
  • Saccharomyces cerevisiae / genetics*


  • Electron Transport Complex IV