Fig. 2.

Crystal structure of a heterodimer between human SOD1 and human CCS (PDB ID: 6FON). CCS is a multidomain protein, and each of the domains is colored differently (gray, green, and blue for domain I, II, and III, respectively). CCS forms a heterodimer with human SOD1 through the SOD1-like domain II, which mimics the homodimerization of SOD1 (also see Fig. 1). Zinc ions bound in SOD1 and also the CCS domain II are colored in magenta, and the Cys residues of CCS involved in the binding of a copper ion (Cys244 and Cys246) are colored yellow.