Binds and deliver cytosolic copper to the copper ATPase proteins. May be important in cellular antioxidant defense (By similarity). Interacts with ATP7B (By similarity). Interacts with ATP7A (By similarity). The heavy-metal-associated domain (HMA) coordinates a Cu(+) ion via the cysteine residues within the CXXC motif. The transfer of Cu(+) ion from ATOX1 to ATP7A involves the formation of a three-coordinate Cu(+)-bridged heterodimer where the metal is shared between the two metal binding sites of ATOX1 and ATP7A. The Cu(+) ion appears to switch between two coordination modes, forming two links with one protein and one with the other. Cisplatin, a chemotherapeutic drug, can bind the CXXC motif and hinder the release of Cu(+) ion. Belongs to the ATX1 family.