Maturation of cytochrome oxidases is a complex process requiring assembly of several subunits and adequate uptake of the metal cofactors. Two orthologous Sco proteins (Sco1 and Sco2) are essential for the correct assembly of the dicopper Cu A site in the human oxidase, but their function is not fully understood. Here, we report an in vitro biochemical study that shows that Sco1 is a metallochaperone that selectively transfers Cu(I) ions based on loop recognition, whereas Sco2 is a copper-dependent thiol reductase of the cysteine ligands in the oxidase. Copper binding to Sco2 is essential to elicit its redox function and as a guardian of the reduced state of its own cysteine residues in the oxidizing environment of the mitochondrial intermembrane space (IMS). These results provide a detailed molecular mechanism for Cu A assembly, suggesting that copper and redox homeostasis are intimately linked in the mitochondrion.
In eukaryotes, cytosolic monothiol glutaredoxins are proteins implicated in intracellular iron trafficking and sensing via their bound [2Fe-2S] clusters. We define a new role of human cytosolic monothiol glutaredoxin-3 (GRX3) in transferring its [2Fe-2S] clusters to human anamorsin, a physical and functional protein partner of GRX3 in the cytosol, whose [2Fe-2S] cluster-bound form is involved in the biogenesis of cytosolic and nuclear Fe-S proteins. Specific protein recognition between the N-terminal domains of the two proteins is the mandatory requisite to promote the [2Fe-2S] cluster transfer from GRX3 to anamorsin.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.