title: Atp23 biogenesis reveals a chaperone-like folding activity of Mia40 in the IMS of mitochondria.
abstract: Mia40 is a recently identified oxidoreductase in the intermembrane space (IMS) of mitochondria that mediates protein import in an oxidation-dependent reaction. Substrates of Mia40 that were identified so far are of simple structure and receive one or two disulphide bonds. Here we identified the protease Atp23 as a novel substrate of Mia40. Atp23 contains ten cysteine residues which are oxidized during several rounds of interaction with Mia40. In contrast to other Mia40 substrates, oxidation of Atp23 is not essential for its import; an Atp23 variant in which all ten cysteine residues were replaced by serine residues still accumulates in mitochondria in a Mia40-dependent manner. In vitro Mia40 can mediate the folding of wild-type Atp23 and prevents its aggregation. In these reactions, the hydrophobic substrate-binding pocket of Mia40 was found to be essential for its chaperone-like activity. Thus, Mia40 plays a much broader role in import and folding of polypeptides than previously expected and can serve as folding factor for proteins with complex disulphide patterns as well as for cysteine-free polypeptides.
authors.affiliation: Division of Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Weckbecker
authors.forename: Sebastian
authors.initials: S
authors.lastname: Longen
authors.forename: Jan
authors.initials: J
authors.lastname: Riemer
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Herrmann
mesh_terms: D045726:Metalloproteases / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D018832:Molecular Chaperones / Q000378:metabolism*; D017510:Protein Folding; D021381:Protein Transport / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: C495320:MIA40 protein, S cerevisiae; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D018832:Molecular Chaperones; D029701:Saccharomyces cerevisiae Proteins; C519195:ATP23 protein, S cerevisiae; D045726:Metalloproteases