title: Oxa1 directly interacts with Atp9 and mediates its assembly into the mitochondrial F1Fo-ATP synthase complex.
abstract: The yeast Oxa1 protein is involved in the biogenesis of the mitochondrial oxidative phosphorylation (OXPHOS) machinery. The involvement of Oxa1 in the assembly of the cytochrome oxidase (COX) complex, where it facilitates the cotranslational membrane insertion of mitochondrially encoded COX subunits, is well documented. In this study we have addressed the role of Oxa1, and its sequence-related protein Cox18/Oxa2, in the biogenesis of the F(1)F(o)-ATP synthase complex. We demonstrate that Oxa1, but not Cox18/Oxa2, directly supports the assembly of the membrane embedded F(o)-sector of the ATP synthase. Oxa1 was found to physically interact with newly synthesized mitochondrially encoded Atp9 protein in a posttranslational manner and in a manner that is not dependent on the C-terminal, matrix-localized region of Oxa1. The stable manner of the Atp9-Oxa1 interaction is in contrast to the cotranslational and transient interaction previously observed for the mitochondrially encoded COX subunits with Oxa1. In the absence of Oxa1, Atp9 was observed to assemble into an oligomeric complex containing F(1)-subunits, but its further assembly with subunit 6 (Atp6) of the F(o)-sector was perturbed. We propose that by directly interacting with newly synthesized Atp9 in a posttranslational manner, Oxa1 is required to maintain the assembly competence of the Atp9-F(1)-subcomplex for its association with Atp6.
authors.affiliation: Department of Biological Sciences, Marquette University, Milwaukee, WI 53233, USA.
authors.forename: Lixia
authors.initials: L
authors.lastname: Jia
authors.forename: Mary K
authors.initials: MK
authors.lastname: Dienhart
authors.forename: Rosemary A
authors.initials: RA
authors.lastname: Stuart
mesh_terms: D003576:Electron Transport Complex IV / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D025261:Mitochondrial Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000737:chemistry; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C501004:ATP6 protein, S cerevisiae; C409465:COX18 protein, S cerevisiae; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; C090858:OXA1 protein; D029701:Saccharomyces cerevisiae Proteins; D003576:Electron Transport Complex IV; D025261:Mitochondrial Proton-Translocating ATPases; C491522:OLI1 protein, S cerevisiae