title: Saccharomyces cerevisiae Coq9 polypeptide is a subunit of the mitochondrial coenzyme Q biosynthetic complex.
abstract: Coenzyme Q (Q) is a redox active lipid that is an essential component of the electron transport chain. Here, we show that steady state levels of Coq3, Coq4, Coq6, Coq7 and Coq9 polypeptides in yeast mitochondria are dependent on the expression of each of the other COQ genes. Submitochondrial localization studies indicate Coq9p is a peripheral membrane protein on the matrix side of the mitochondrial inner membrane. To investigate whether Coq9p is a component of a complex of Q-biosynthetic proteins, the native molecular mass of Coq9p was determined by Blue Native-PAGE. Coq9p was found to co-migrate with Coq3p and Coq4p at a molecular mass of approximately 1 MDa. A direct physical interaction was shown by the immunoprecipitation of HA-tagged Coq9 polypeptide with Coq4p, Coq5p, Coq6p and Coq7p. These findings, together with other work identifying Coq3p and Coq4p interactions, identify at least six Coq polypeptides in a multi-subunit Q biosynthetic complex.
authors: Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors: Edward J
authors: EJ
authors: Hsieh
authors: Peter
authors: P
authors: Gin
authors: Melissa
authors: M
authors: Gulmezian
authors: UyenPhuong C
authors: UC
authors: Tran
authors: Ryoichi
authors: R
authors: Saiki
authors: Beth N
authors: BN
authors: Marbois
authors: Catherine F
authors: CF
authors: Clarke
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D051336:Mitochondrial Membranes / Q000737:chemistry; D024101:Mitochondrial Proteins / Q000737:chemistry*; D009097:Multienzyme Complexes / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*; D014451:Ubiquinone / Q000096:biosynthesis* / Q000737:chemistry
chemical_list: C521712:Coq9 protein, S cerevisiae; D024101:Mitochondrial Proteins; D009097:Multienzyme Complexes; D029701:Saccharomyces cerevisiae Proteins; D014451:Ubiquinone; C030571:ubiquinone 9