Copper chaperone for superoxide dismutase is a metalloprotein that is responsible for the delivery of Cu to superoxide dismutase (SOD1). CCS is a 54kDa protein that is present in mammals and most eukaryotes including yeast. The structure of CCS is composed of three distinct domains that are necessary for its function. Although CCS is important for many organisms, there are CCS independent pathways for SOD1, and many species lack CCS all together, such as C. elegans. In humans the protein is encoded by the CCS gene.