2l0y
Complex hMia40-hCox17Complex hMia40-hCox17
Structural highlights
FunctionMIA40_HUMAN Functions as chaperone and catalyzes the formation of disulfide bonds in substrate proteins, such as COX17. Required for the import and folding of small cysteine-containing proteins (small Tim) in the mitochondrial intermembrane space (IMS). Precursor proteins to be imported into the IMS are translocated in their reduced form into the mitochondria. The oxidized form of CHCHD4/MIA40 forms a transient intermolecular disulfide bridge with the reduced precursor protein, resulting in oxidation of the precursor protein that now contains an intramolecular disulfide bond and is able to undergo folding in the IMS. Reduced CHCHD4/MIA40 is then reoxidized by GFER/ERV1 via a disulfide relay system.[1] [2] [3] [4] Publication Abstract from PubMedSeveral proteins of the mitochondrial intermembrane space are targeted by internal targeting signals. A class of such proteins with alpha-helical hairpin structure bridged by two intramolecular disulfides is trapped by a Mia40-dependent oxidative process. Here, we describe the oxidative folding mechanism underpinning this process by an exhaustive structural characterization of the protein in all stages and as a complex with Mia40. Two consecutive induced folding steps are at the basis of the protein-trapping process. In the first one, Mia40 functions as a molecular chaperone assisting alpha-helical folding of the internal targeting signal of the substrate. Subsequently, in a Mia40-independent manner, folding of the second substrate helix is induced by the folded targeting signal functioning as a folding scaffold. The Mia40-induced folding pathway provides a proof of principle for the general concept that internal targeting signals may operate as a folding nucleus upon compartment-specific activation. Molecular chaperone function of Mia40 triggers consecutive induced folding steps of the substrate in mitochondrial protein import.,Banci L, Bertini I, Cefaro C, Cenacchi L, Ciofi-Baffoni S, Felli IC, Gallo A, Gonnelli L, Luchinat E, Sideris D, Tokatlidis K Proc Natl Acad Sci U S A. 2010 Nov 8. PMID:21059946[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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