Precursor oxidation by Mia40 and Erv1 promotes vectorial transport of proteins into the mitochondrial intermembrane space.
The mitochondrial intermembrane space contains chaperone complexes that guide hydrophobic precursor proteins through this aqueous compartment. The chaperones consist of hetero-oligomeric complexes of small Tim proteins with conserved cysteine residues. The precursors of small Tim proteins are synthesized in the cytosol. Import of the precursors requires the essential intermembrane space proteins Mia40 and Erv1 that were proposed to form a relay for disulfide formation in the precursor proteins. However, experimental evidence for a role of Mia40 and Erv1 in the oxidation of intermembrane space precursors has been lacking. We have established a system to directly monitor the oxidation of precursors during import into mitochondria and dissected distinct steps of the import process. Reduced precursors bind to Mia40 during translocation into mitochondria. Both Mia40 and Erv1 are required for formation of oxidized monomers of the precursors that subsequently assemble into oligomeric complexes. Whereas the reduced precursors can diffuse back into the cytosol, the oxidized precursors are retained in the intermembrane space. Thus, oxidation driven by Mia40 and Erv1 determines vectorial transport of the precursors into the mitochondrial intermembrane space.
Müller
Judith M
JM
Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Universität Freiburg, D-79104 Freiburg, Germany.
Milenkovic
Dusanka
D
Guiard
Bernard
B
Pfanner
Nikolaus
N
Chacinska
Agnieszka
A
D003545:Cysteine; D004220:Disulfides / Q000378:metabolism; D026901:Membrane Transport Proteins / 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; D024101:Mitochondrial Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction; D050862:Oxidoreductases Acting on Sulfur Group Donors; D011498:Protein Precursors / Q000378:metabolism*; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
D004220:Disulfides; C495320:MIA40 protein, S cerevisiae; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D011498:Protein Precursors; D029701:Saccharomyces cerevisiae Proteins; C519190:Tim8 protein, S cerevisiae; D050862:Oxidoreductases Acting on Sulfur Group Donors; C073790:ERV1 protein, S cerevisiae; D003545:Cysteine