title: Import of the cytochrome oxidase subunit Va precursor into yeast mitochondria is mediated by the outer membrane receptor Mas20p.
abstract: Post-translational import of precursor proteins into yeast mitochondria is mediated by at least four protease-sensitive outer membrane proteins: Mas20p, Mas22p, Mas37p, and Mas70p. These "import receptors" recognize either the N-terminal targeting signal or some other feature of mitochondrial precursor proteins. The only exception to this general rule appeared to be the precursor to subunit Va of cytochrome c oxidase (COXVa). Although this precursor carries a typical N-terminal mitochondrial targeting sequence, its import into mitochondria has been suggested to be independent of the known import receptors. Here we show that if import into isolated yeast mitochondria is assayed under conditions in which binding of the COXVa precursor to mitochondria is rate-limiting, import is strongly inhibited by protease pretreatment of the mitochondria or by antibodies against Mas20p. Post-translational import of the COXVa precursor can thus proceed by the general, receptor-mediated pathway.
authors.affiliation: Biozentrum, University of Basel, Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Lithgow
authors.forename: G
authors.initials: G
authors.lastname: Schatz
mesh_terms: D001692:Biological Transport; D003576:Electron Transport Complex IV / Q000378:metabolism*; D004792:Enzyme Precursors / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D004792:Enzyme Precursors; D008565:Membrane Proteins; D033681:Mitochondrial Membrane Transport Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; C489350:TOM20 protein, S cerevisiae; D003576:Electron Transport Complex IV