title: MAS6 encodes an essential inner membrane component of the yeast mitochondrial protein import pathway.
abstract: To identify new components that mediate mitochondrial protein import, we analyzed mas6, an import mutant in the yeast Saccharomyces cerevisiae. mas6 mutants are temperature sensitive for viability, and accumulate mitochondrial precursor proteins at the restrictive temperature. We show that mas6 does not correspond to any of the presently identified import mutants, and we find that mitochondria isolated from mas6 mutants are defective at an early stage of the mitochondrial protein import pathway. MAS6 encodes a 23-kD protein that contains several potential membrane spanning domains, and yeast strains disrupted for MAS6 are inviable at all temperatures and on all carbon sources. The Mas6 protein is located in the mitochondrial inner membrane and cannot be extracted from the membrane by alkali treatment. Antibodies to the Mas6 protein inhibit import into isolated mitochondria, but only when the outer membrane has been disrupted by osmotic shock. Mas6p therefore represents an essential import component located in the mitochondrial inner membrane.
authors.affiliation: Department of Cell Biology and Anatomy, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
authors.forename: J L
authors.initials: JL
authors.lastname: Emtage
authors.forename: R E
authors.initials: RE
authors.lastname: Jensen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000032:analysis* / Q000235:genetics* / Q000502:physiology; D004247:DNA / Q000032:analysis / Q000235:genetics; D005796:Genes / Q000235:genetics*; D006360:Heat-Shock Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology; D007106:Immune Sera; D007425:Intracellular Membranes / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D008565:Membrane Proteins / Q000032:analysis* / Q000235:genetics* / Q000502:physiology; D026901:Membrane Transport Proteins; D016253:Microscopy, Immunoelectron; D008928:Mitochondria / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011233:Precipitin Tests; D011498:Protein Precursors / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D002352:Carrier Proteins; D006360:Heat-Shock Proteins; D007106:Immune Sera; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D011498:Protein Precursors; D029701:Saccharomyces cerevisiae Proteins; C083081:TIM23 protein, S cerevisiae; D004247:DNA