CHAPTER 3.2: Disulfide Bond Formation in Mitochondria

The mitochondrial intermembrane space (IMS) harbors many proteins with structural disulfide bonds that are formed during or directly subsequent to their import from the cytosol. Oxidative protein folding in the IMS relies on two essential components: the oxidoreductase Mia40 (CHCHD4 in mammals) and the sulfhydryl oxidase Erv1 (ALR in mammals). Mia40 has two distinct functions. First, it serves as an import receptor that drives protein translocation across the outer membrane by binding hydrophobic patches of unfolded incoming polypeptides, and second, it introduces disulfide bonds into many of these proteins and facilitates their stable folding. The flavoprotein Erv1 maintains Mia40 in an oxidized and active state. The components of the mitochondrial disulfide relay and its substrates are discussed in this chapter.