The Mitochondrial Intermembrane Space Oxireductase Mia40 Funnels the Oxidative Folding Pathway of the Cytochrome c Oxidase Assembly Protein Cox19 |
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Authors: | Hugo Fraga Joan-Josep Bech-Serra Francesc Canals Gabriel Ortega Oscar Millet Salvador Ventura |
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Affiliation: | From the ‡Institut de Biotecnologia i Biomedicina and ;§Departament de Bioquimica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain.;¶Vall d''Hebron Institute of Oncology (VHIO), Vall d''Hebron University Hospital, 08135 Barcelona, Spain, and ;‖Metabolism and Disease Program, Structural Biology Unit, CIC bioGUNE, Bizkaia Technology Park, Bld. 800, 48160 Derio, Spain |
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Abstract: | Mia40-catalyzed disulfide formation drives the import of many proteins into the mitochondria. Here we characterize the oxidative folding of Cox19, a twin CX9C Mia40 substrate. Cox19 oxidation is extremely slow, explaining the persistence of import-competent reduced species in the cytosol. Mia40 accelerates Cox19 folding through the specific recognition of the third Cys in the second helical CX9C motif and the subsequent oxidation of the inner disulfide bond. This renders a native-like intermediate that oxidizes in a slow uncatalyzed reaction into native Cox19. The same intermediate dominates the pathway in the absence of Mia40, and chemical induction of an α-helical structure by trifluoroethanol suffices to accelerate productive folding and mimic the Mia40 folding template mechanism. The Mia40 role is to funnel a rough folding landscape, skipping the accumulation of kinetic traps, providing a rationale for the promiscuity of Mia40. |
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Keywords: | Biophysics Disulfide Mitochondria Oxidation-Reduction Protein Folding Protein Translocation Cox19 Mia40 Protein Oxidative Folding |
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