title: Oxa1p, an essential component of the N-tail protein export machinery in mitochondria.
abstract: A number of nuclear encoded inner membrane proteins of mitochondria span the membrane in such a manner that their N termini are located in the intermembrane space. Many of these proteins attain this membrane orientation by undergoing an export step from the matrix across the inner membrane. This export process, which resembles bacterial N-tail export from energetic and topogenic signal requirements, is facilitated by Oxa1p, a protein that has homologues throughout prokaryotes and eukaryotes. Oxa1p, as we have previously shown, is required to export the N and C termini of the mitochondrially encoded pCoxII to the intermembrane space. We demonstrate here that imported nuclear encoded proteins physically interact with Oxa1p and depend on Oxa1p for efficient export of their N termini to the intermembrane space. Furthermore, Oxa1p interacts with nascent polypeptide chains synthesized in mitochondria, including the fully synthesized pCoxII and CoxIII species. Thus, Oxa1p represents a component of a general export machinery of the mitochondrial inner membrane.
authors.affiliation: Institut für Physiologische Chemie der Universität München, Goethestrasse 33, 80336 Munich, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Hell
authors.forename: J M
authors.initials: JM
authors.lastname: Herrmann
authors.forename: E
authors.initials: E
authors.lastname: Pratje
authors.forename: W
authors.initials: W
authors.lastname: Neupert
authors.forename: R A
authors.initials: RA
authors.lastname: Stuart
mesh_terms: D003432:Cross-Linking Reagents; D003576:Electron Transport Complex IV / Q000096:biosynthesis / Q000378:metabolism; D005656:Fungal Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D008958:Models, Molecular; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis; D011487:Protein Conformation; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013762:Tetrahydrofolate Dehydrogenase / Q000096:biosynthesis / Q000378:metabolism
chemical_list: D003432:Cross-Linking Reagents; D005656:Fungal Proteins; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; C090858:OXA1 protein; D011498:Protein Precursors; D011993:Recombinant Fusion Proteins; D013762:Tetrahydrofolate Dehydrogenase; D003576:Electron Transport Complex IV