PROS1 and Wilson disease: In humans, the 68-residue Cu+ chaperone Atox1 picks up Cu+ that has entered the cell via CTR1 and delivers the metal to cytoplasmic metal-binding domains in ATP7A and ATP7B (also called Menke’s and Wilson disease proteins, respectively), two homologous multidomain P1B-type ATPases located in the trans-Golgi network.