Tom71, a novel homologue of the mitochondrial preprotein receptor Tom70.
The protein Tom71 is encoded by the open reading frame YHR117w (yeast chromosome VIII) and shares 53% amino acid sequence identity with Tom70, a protein import receptor of the mitochondrial outer membrane. We investigated the cellular function of Tom71 and addressed the question of whether Tom71 and Tom70 fulfill similar functions. Like Tom70, Tom71 is anchored to the mitochondrial outer membrane via its N terminus, thereby exposing a large C-terminal domain to the cytosol. Tom71 is associated with the protein import complex of this membrane and can be cross-linked to a protein with a molecular mass of 30-35 kDa. Disruption of the TOM71 gene does not reduce cell growth, except on nonfermentable carbon sources at elevated temperatures. Deletion of both the TOM71 and TOM70 genes does not acerbate this growth defect. In vitro import studies demonstrated no functional requirement for Tom71 in the import of several preproteins destined for each of the mitochondrial subcompartments. In particular, the import of Tom70-dependent preproteins is minimally affected by the deletion of Tom71, irrespective of the presence or absence of the Tom70 receptor. Thus, despite their strikingly similar biochemical properties, Tom71 and Tom70 do not perform identical functions.
Schlossmann
J
J
Institut für Physiologische Chemie, Physikalische Biochemie und Zellbiologie der Universität München, Goethestrasse 33, 80 336 München, Germany.
Lill
R
R
Neupert
W
W
Court
D A
DA
D000595:Amino Acid Sequence; D001692:Biological Transport; D003432:Cross-Linking Reagents; D005656:Fungal Proteins / Q000235:genetics*; D005800:Genes, Fungal; D008565:Membrane Proteins / Q000235:genetics; D008928:Mitochondria / Q000235:genetics*; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008969:Molecular Sequence Data; D011485:Protein Binding; D011498:Protein Precursors / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid
D003432:Cross-Linking Reagents; D005656:Fungal Proteins; D008565:Membrane Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D011498:Protein Precursors; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; C489039:TOM70 protein, S cerevisiae; D000226:Mitochondrial ADP, ATP Translocases