Copper ion transmembrane transporter involved in the export of copper out of the cells, such as the efflux of hepatic copper into the bile. ATP + Cu(+)(in) + H2O = ADP + Cu(+)(out) + H(+) + phosphate Monomer. Interacts with COMMD1/MURR1 (By similarity). Interacts with DCTN4, in a copper-dependent manner (By similarity). Interacts with ATOX1 (By similarity). Interacts (via C-terminus) with ZBTB16/PLZF (By similarity). Predominantly found in the trans-Golgi network (TGN). Not redistributed to the plasma membrane in response to elevated copper levels. Detected in liver and kidney. Each HMA domain can bind a copper ion, they are tightly packed and closely interact with each other. Wild-type ATP7B can usually be loaded with an average 5.5 copper atoms per molecule (By similarity). Defects in Atp7b are the cause of the toxic milk mouse mutant (tx) phenotype, characterized by accumulation of copper in the liver in a manner similar to that observed in patients with Wilson disease. Belongs to the cation transport ATPase (P-type) (TC 3.A.3) family. Type IB subfamily.