title: Mia40 targets cysteines in a hydrophobic environment to direct oxidative protein folding in the mitochondria.
abstract: Mia40 catalyses the oxidative folding of disulphide-containing proteins in the mitochondria. The folding pathway is directed by the formation of the first mixed disulphide between Mia40 and its substrate. Here, we employ Cox17 to elucidate the molecular determinants of this reaction. Mia40 engages initially in a dynamic non-covalent enzyme-substrate complex that forms and dissociates within milliseconds. Cys36 of Cox17 forms the mixed disulphide in an extremely rapid reaction that is limited by the preceding complex formation with Mia40. Cys36 reacts much faster than the three other cysteines of Cox17, because it neighbours three hydrophobic residues. Mia40 binds preferentially to hydrophobic regions and the dynamic nature of the non-covalent complex allows rapid reorientation for an optimal positioning of the reactive cysteine. Mia40 thus uses the unique proximity between its substrate-binding site and the catalytic disulphide to select a particular cysteine for forming the critical initial mixed disulphide.
authors.affiliation: Laboratorium für Biochemie und Bayreuther Zentrum für Molekulare Biologie, Universität Bayreuth, 95440 Bayreuth, Germany.
authors.forename: Johanna R
authors.initials: JR
authors.lastname: Koch
authors.affiliation: Laboratorium für Biochemie und Bayreuther Zentrum für Molekulare Biologie, Universität Bayreuth, 95440 Bayreuth, Germany.
authors.forename: Franz X
authors.initials: FX
authors.lastname: Schmid
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D027682:Cation Transport Proteins / Q000737:chemistry / Q000502:physiology; D000079922:Copper Transport Proteins; D003545:Cysteine / Q000502:physiology*; D004220:Disulfides; D057927:Hydrophobic and Hydrophilic Interactions; D008928:Mitochondria / Q000502:physiology; D033681:Mitochondrial Membrane Transport Proteins / Q000737:chemistry / Q000502:physiology*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000502:physiology*; D008954:Models, Biological; D018832:Molecular Chaperones / Q000737:chemistry / Q000502:physiology; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D017510:Protein Folding; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000502:physiology*
chemical_list: C100359:COX17 protein, S cerevisiae; D027682:Cation Transport Proteins; D000079922:Copper Transport Proteins; D004220:Disulfides; C495320:MIA40 protein, S cerevisiae; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D018832:Molecular Chaperones; D029701:Saccharomyces cerevisiae Proteins; D003545:Cysteine