title: Genetic evidence for a multi-subunit complex in coenzyme Q biosynthesis in yeast and the role of the Coq1 hexaprenyl diphosphate synthase.
abstract: Coenzyme Q (Q) is a lipid that functions as an electron carrier in the mitochondrial respiratory chain in eukaryotes. There are eight complementation groups of Q-deficient Saccharomyces cerevisiae mutants designated coq1-coq8. Here we provide genetic evidence that several of the Coq polypeptides interact with one another. Deletions in any of the COQ genes affect the steady-state expression of Coq3p, Coq4p, and Coq6p. Antibodies that recognize Coq1p, a hexaprenyl diphosphate synthase, were generated and used to determine that Coq1p is peripherally associated with the inner membrane on the matrix side. Yeast Deltacoq1 mutants harboring diverse Coq1 orthologs from prokaryotic species produce distinct sizes of polyprenyl diphosphate and hence distinct isoforms of Q including Q(7), Q(8), Q(9), or Q(10) (Okada, K., Kainou, T., Matsuda, H., and Kawamukai, M. (1998) FEBS Lett. 431, 241-244). We find that steady-state levels of Coq3p, Coq4p, and Coq6p are rescued in some cases to near wild-type levels by the presence of these diverse Coq1 orthologs in the Deltacoq1 mutant. These data suggest that the lipid product of Coq1p or a Q-intermediate derived from polyprenyl diphosphate is involved in stabilizing the Coq3, Coq4, and Coq6 polypeptides.
authors.affiliation: Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, California 90095, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Gin
authors.forename: Catherine F
authors.initials: CF
authors.lastname: Clarke
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000502:physiology*; D000595:Amino Acid Sequence; D049109:Cell Proliferation; D004926:Escherichia coli / Q000378:metabolism; D005838:Genotype; D015151:Immunoblotting; D008928:Mitochondria / Q000378:metabolism; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry*; D009154:Mutation; D016366:Open Reading Frames; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D014451:Ubiquinone / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*
chemical_list: D009097:Multienzyme Complexes; D010455:Peptides; D020033:Protein Isoforms; D029701:Saccharomyces cerevisiae Proteins; D014451:Ubiquinone; D019883:Alkyl and Aryl Transferases; C036826:trans-pentaprenyltranstransferase; C025203:Ubiquinone Q1