Genetic evidence for a multi-subunit complex in the O-methyltransferase steps of coenzyme Q biosynthesis

Biochim Biophys Acta. 2000 Apr 12;1484(2-3):287-97. doi: 10.1016/s1388-1981(00)00019-6.

Abstract

Coq3 O-methyltransferase carries out both O-methylation steps in coenzyme Q (ubiquinone) biosynthesis. The degree to which Coq3 O-methyltransferase activity and expression are dependent on the other seven COQ gene products has been investigated. A panel of yeast mutant strains harboring null mutations in each of the genes required for coenzyme Q biosynthesis (COQ1-COQ8) have been prepared. Mitochondria have been isolated from each member of the yeast coq mutant collection, from the wild-type parental strains and from respiratory deficient mutants harboring deletions in ATP2 or COR1 genes. These latter strains constitute Q-replete, respiratory deficient controls. Each of these mitochondrial preparations has been analyzed for COQ3-encoded O-methyltransferase activity and steady state levels of Coq3 polypeptide. The findings indicate that the presence of the other COQ gene products is required to observe normal levels of O-methyltransferase activity and the Coq3 polypeptide. However, COQ3 steady state RNA levels are not decreased in any of the coq mutants, relative to either wild-type or respiratory deficient control strains, suggesting either a decreased rate of translation or a decreased stability of the Coq3 polypeptide. These data are consistent with the involvement of the Coq polypeptides (or the Q-intermediates formed by the Coq polypeptides) in a multi-subunit complex. It is our hypothesis that a deficiency in any one of the COQ gene products results in a defective complex in which the Coq3 polypeptide is rendered unstable.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Enzyme Stability / genetics
  • Gene Deletion
  • Genotype
  • Methyltransferases / biosynthesis
  • Methyltransferases / chemistry
  • Methyltransferases / metabolism*
  • Mutation
  • RNA / biosynthesis
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Ubiquinone / biosynthesis*
  • Ubiquinone / chemistry
  • Ubiquinone / deficiency

Substances

  • ubiquinone Q3
  • Ubiquinone
  • RNA
  • Methyltransferases
  • 3,4-dihydroxy-5-hexaprenylbenzoate methyltransferase