Solution Structure of CopC: A Cupredoxin-like Protein Involved in Copper Homeostasis

The structure of the metal-free form of CopC, a protein involved in copper homeostasis, has been obtained. The fold is a Greek key β barrel similar to that of functionally unrelated blue copper proteins but with important structural variations. The protein binds one equivalent of copper (II) with relatively high affinity and contains a cluster of conserved residues (His1, Glu27, Asp89, and His91) which could form a water-accessible metal binding site. The structure also reveals a loop containing the M(X) nM motif which is present in a number of proteins also involved in copper homeostasis. The present structure represents a link between copper-trafficking proteins and cupredoxins. Within a structural and genomic analysis, the role of CopC in copper trafficking is discussed.