title: Mitochondrial protein import: Mia40 facilitates Tim22 translocation into the inner membrane of mitochondria.
abstract: The mitochondrial intermembrane space assembly (MIA) pathway is generally considered to be dedicated to the redox-dependent import and biogenesis of proteins localized to the intermembrane space of mitochondria. The oxidoreductase Mia40 is a central component of the pathway responsible for the transfer of disulfide bonds to intermembrane space precursor proteins, causing their oxidative folding. Here we present the first evidence that the function of Mia40 is not restricted to the transport and oxidative folding of intermembrane space proteins. We identify Tim22, a multispanning membrane protein and core component of the TIM22 translocase of inner membrane, as a protein with cysteine residues undergoing oxidation during Tim22 biogenesis. We show that Mia40 is involved in the biogenesis and complex assembly of Tim22. Tim22 forms a disulfide-bonded intermediate with Mia40 upon import into mitochondria. Of interest, Mia40 binds the Tim22 precursor also via noncovalent interactions. We propose that Mia40 not only is responsible for disulfide bond formation, but also assists the Tim22 protein in its integration into the inner membrane of mitochondria.
authors.affiliation: International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland.
authors.forename: Lidia
authors.initials: L
authors.lastname: Wrobel
authors.forename: Agata
authors.initials: A
authors.lastname: Trojanowska
authors.forename: Malgorzata E
authors.initials: ME
authors.lastname: Sztolsztener
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Chacinska
mesh_terms: D003545:Cysteine / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism*; D009154:Mutation; D010084:Oxidation-Reduction; D017510:Protein Folding; D021381:Protein Transport / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C495320:MIA40 protein, S cerevisiae; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins; C102549:TIM22 protein, S cerevisiae; D003545:Cysteine