title: Intramolecular disulfide bond of Tim22 protein maintains integrity of the TIM22 complex in the mitochondrial inner membrane.
abstract: Mitochondrial proteins require protein machineries called translocators in the outer and inner membranes for import into and sorting to their destination submitochondrial compartments. Among them, the TIM22 complex mediates insertion of polytopic membrane proteins into the inner membrane, and Tim22 constitutes its central insertion channel. Here we report that the conserved Cys residues of Tim22 form an intramolecular disulfide bond. By comparison of Tim22 Cys → Ser mutants with wild-type Tim22, we show that the disulfide bond of Tim22 stabilizes Tim22 especially at elevated temperature through interactions with Tim18, which are also important for the stability of the TIM22 complex. We also show that lack of the disulfide bond in Tim22 impairs the assembly of TIM22 pathway substrate proteins into the inner membrane especially when the TIM22 complex handles excess amounts of substrate proteins. Our findings provide a new insight into the mechanism of the maintenance of the structural and functional integrity of the TIM22 complex.
authors.affiliation: From the Department of Chemistry, Graduate School of Science.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Okamoto
authors.forename: Akiko
authors.initials: A
authors.lastname: Miyagawa
authors.forename: Takuya
authors.initials: T
authors.lastname: Shiota
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Tamura
authors.forename: Toshiya
authors.initials: T
authors.lastname: Endo
mesh_terms: D000595:Amino Acid Sequence; D017920:Antiporters / Q000378:metabolism; D003545:Cysteine / Q000235:genetics; D004220:Disulfides / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008954:Models, Biological; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D055550:Protein Stability; D021381:Protein Transport; D059748:Proteolysis; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D012694:Serine / Q000235:genetics; D013696:Temperature
chemical_list: D017920:Antiporters; D004220:Disulfides; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D046912:Multiprotein Complexes; D050505:Mutant Proteins; D029701:Saccharomyces cerevisiae Proteins; C102549:TIM22 protein, S cerevisiae; C403803:Tim18 protein, S cerevisiae; D012694:Serine; D003545:Cysteine
keywords: Disulfide; Membrane Proteins; Mitochondria; Protein Translocation; Tim22; Yeast