Binds and deliver cytosolic copper to the copper ATPase proteins. May be important in cellular antioxidant defense. Interacts with ATP7B (PubMed:10966647). Interacts with ATP7A (PubMed:21667063, PubMed:19453293). Ubiquitous. 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.