Copper chaperone for apo superoxide dismutase 1 (SOD1). Binds copper ions and delivers them specifically to apo-SOD1. Binds 2 copper ions per subunit. Homodimer, and heterodimer with apo-SOD1. Zinc-binding at His-16 of CCS1 and 'Glu-43' of apo-SOD1 is required for this heterodimerization. A small percentage (around 1-5 percent) localizes to the mitochondrial intermembrane space. Present with 12000 molecules/cell in log phase SD medium. Belongs to the CCS1 family.