Figure 3.

Import of cysteine-containing precursor proteins into the IMS. The Mia40 receptor forms transient intermolecular disulfide bonds with precursors emerging from the TOM complex. Mia40 functions not only as a receptor, but also as an oxidoreductase by catalyzing the formation of intramolecular disulfide bonds within the precursor together with the sulfhydryl oxidase Erv1. A ternary complex of Mia40, Erv1, and a bound precursor protein allows for the incorporation of multiple disulfide bonds. Erv1 re-oxidizes Mia40 for another round of import and transfers electrons via cytochrome c (Cyt.c) and cytochrome c oxidase (COX) to molecular oxygen. OM, outer membrane; IMS, intermembrane space; IM, inner membrane.