A novel intermembrane space–targeting signal docks cysteines onto Mia40 during mitochondrial oxidative folding

作者：Dionisia P. Sideris, Nikos Petrakis, Nitsa Katrakili, Despina Mikropoulou, Angelo Gallo, Simone Ciofi‐Baffoni, Lucia Banci, Ivano Bertini, Kostas Tokatlidis · 发表于：The Journal of Cell Biology · 年份：2009 · DOI：10.1083/jcb.200905134 · 被引用次数：178 · 研究领域：Mitochondrial Function and Pathology、ATP Synthase and ATPases Research、Redox biology and oxidative stress

Mia40 imports Cys-containing proteins into the mitochondrial intermembrane space (IMS) by ensuring their Cys-dependent oxidative folding. In this study, we show that the specific Cys of the substrate involved in docking with Mia40 is substrate dependent, the process being guided by an IMS-targeting signal (ITS) present in Mia40 substrates. The ITS is a 9-aa internal peptide that (a) is upstream or downstream of the docking Cys, (b) is sufficient for crossing the outer membrane and for targeting nonmitochondrial proteins, (c) forms an amphipathic helix with crucial hydrophobic residues on the side of the docking Cys and dispensable charged residues on the other side, and (d) fits complementary to the substrate cleft of Mia40 via hydrophobic interactions of micromolar affinity. We rationalize the dual function of Mia40 as a receptor and an oxidase in a two step-specific mechanism: an ITS-guided sliding step orients the substrate noncovalently, followed by docking of the substrate Cys now juxtaposed to pair with the Mia40 active Cys.