title: Integral membrane proteins in the mitochondrial outer membrane of Saccharomyces cerevisiae.
abstract: Mitochondria evolved from a bacterial endosymbiont ancestor in which the integral outer membrane proteins would have been beta-barrel structured within the plane of the membrane. Initial proteomics on the outer membrane from yeast mitochondria suggest that while most of the protein components are integral in the membrane, most of these mitochondrial proteins behave as if they have alpha-helical transmembrane domains, rather than beta-barrels. These proteins are usually predicted to have a single alpha-helical transmembrane segment at either the N- or C-terminus, however, more complex topologies are also seen. We purified the novel outer membrane protein Om14 and show it is encoded in the gene YBR230c. Protein sequencing revealed an intron is spliced from the transcript, and both transcription from the YBR230c gene and steady-state level of the Om14 protein is dramatically less in cells grown on glucose than in cells grown on nonfermentable carbon sources. Hydropathy predictions together with data from limited protease digestion show three alpha-helical transmembrane segments in Om14. The alpha-helical outer membrane proteins provide functions derived after the endosymbiotic event, and require the translocase in the outer mitochondrial membrane complex for insertion into the outer membrane.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Australia.
authors.forename: Lena
authors.initials: L
authors.lastname: Burri
authors.forename: Katherine
authors.initials: K
authors.lastname: Vascotto
authors.forename: Ian E
authors.initials: IE
authors.lastname: Gentle
authors.forename: Nickie C
authors.initials: NC
authors.lastname: Chan
authors.forename: Traude
authors.initials: T
authors.lastname: Beilharz
authors.forename: David I
authors.initials: DI
authors.lastname: Stapleton
authors.forename: Lynn
authors.initials: L
authors.lastname: Ramage
authors.forename: Trevor
authors.initials: T
authors.lastname: Lithgow
mesh_terms: D000595:Amino Acid Sequence; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins