Identification of Tim40 that mediates protein sorting to the mitochondrial intermembrane space.
Most mitochondrial proteins are synthesized in the cytosol, imported into mitochondria, and sorted to one of the four mitochondrial subcompartments. Here we identified a new inner membrane protein, Tim40, that mediates sorting of small Tim proteins to the intermembrane space. Tim40 is essential for yeast cell growth, and its function in vivo requires six conserved Cys residues but not anchoring of the protein to the inner membrane by its N-terminal hydrophobic segment. Depletion of Tim40 impairs the import of small Tim proteins into mitochondria both in vivo and in vitro. In wild-type mitochondria, Tim40 forms a translocation intermediate with small Tim proteins prior to their assembly in the intermembrane space in vitro. These results suggest the essential role of Tim40 in sorting/assembly of small Tim proteins.
Naoé
Mari
M
Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
Ohwa
Yukimasa
Y
Ishikawa
Daigo
D
Ohshima
Chié
C
Nishikawa
Shuh-Ichi
S
Yamamoto
Hayashi
H
Endo
Toshiya
T
D000595:Amino Acid Sequence; D026901:Membrane Transport Proteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D021381:Protein Transport / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
C495320:MIA40 protein, S cerevisiae; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins; C116366:Tim9 protein, S cerevisiae