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. The short isoform is expressed primarily in the liver with lower levels present in the intestine, hypothalamus and ovary. The long isoform is expressed in the liver. 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). Belongs to the cation transport ATPase (P-type) (TC 3.A.3) family. Type IB subfamily.