title: Assembly of the rotor component of yeast mitochondrial ATP synthase is enhanced when Atp9p is supplied by Atp9p-Cox6p complexes.
abstract: The Atp9p ring is one of several assembly modules of yeast mitochondrial ATP synthase. The ring, composed of 10 copies of Atp9p, is part of the rotor that couples proton translocation to synthesis or hydrolysis of ATP. We present evidence that before its assembly with other ATP synthase modules, most of Atp9p is present in at least three complexes with masses of 200-400 kDa that co-immunopurify with Cox6p. Pulse-labeling analysis disclosed a time-dependent reduction of radiolabeled Atp9p in the complexes and an increase of Atp9p in the ring form of wild type yeast and of mss51, pet111, and pet494 mutants lacking Cox1p, Cox2p, and Cox3p, respectively. Ring formation was not significantly different from wild type in an mss51 or atp10 mutant. The atp10 mutation blocks the interaction of the Atp9p ring with other modules of the ATP synthase. In contrast, ring formation was reduced in a cox6 mutant, consistent with a role of Cox6p in oligomerization of Atp9p. Cox6p involvement in ATP synthase assembly is also supported by studies showing that ring formation in cells adapting from fermentative to aerobic growth was less efficient in mitochondria of the cox6 mutant than the parental respiratory-competent strain or a cox4 mutant. We speculate that the constitutive and Cox6p-independent rate of Atp9p oligomerization may be sufficient to produce the level of ATP synthase needed for maintaining a membrane potential but limiting for optimal oxidative phosphorylation.
authors.affiliation: From the Department of Biological Sciences, Columbia University, New York, New York 10128 and.
authors.forename: Chen-Hsien
authors.initials: CH
authors.lastname: Su
authors.affiliation: Department of Life Sciences, New York Institute of Technology, Old Westbury, New York 11568.
authors.forename: Gavin P
authors.initials: GP
authors.lastname: McStay
authors.affiliation: From the Department of Biological Sciences, Columbia University, New York, New York 10128 and spud@columbia.edu.
authors.forename: Alexander
authors.initials: A
authors.lastname: Tzagoloff
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000332:Aerobiosis; D004272:DNA, Mitochondrial / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D005838:Genotype; D005947:Glucose / Q000378:metabolism; D008564:Membrane Potentials; D008928:Mitochondria / Q000201:enzymology; D025261:Mitochondrial Proton-Translocating ATPases / Q000378:metabolism*; D009154:Mutation; D010085:Oxidative Phosphorylation; D010100:Oxygen / Q000378:metabolism; D010766:Phosphorylation; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D004272:DNA, Mitochondrial; D029701:Saccharomyces cerevisiae Proteins; D000255:Adenosine Triphosphate; D011451:Prostaglandin-Endoperoxide Synthases; C000594391:Cox6 protein, S cerevisiae; D003576:Electron Transport Complex IV; D025261:Mitochondrial Proton-Translocating ATPases; C491522:OLI1 protein, S cerevisiae; D005947:Glucose; D010100:Oxygen
keywords: ATP Synthase; Cytochrome Oxidase; Membrane Biogenesis; Mitochondria; Protein Assembly; Saccharomyces cerevisiae