The ATP7B gene provides instructions for making a protein called copper-transporting ATPase 2. This protein is part of the P-type ATPase family, a group of proteins that transport metals into and out of cells by using energy stored in the molecule adenosine triphosphate (ATP). Copper-transporting ATPase 2 is found primarily in the liver, with smaller amounts in the kidneys and brain. It plays a role in the transport of copper from the liver to other parts of the body. Copper is an important part of certain enzymes that maintain normal cell functions. Copper-transporting ATPase 2 is also important for the removal of excess copper from the body.~Within liver cells, copper-transporting ATPase 2 is found in a structure called the Golgi apparatus, which modifies newly produced enzymes and other proteins. Here, copper-transporting ATPase 2 supplies copper to a protein called ceruloplasmin, which transports copper to other parts of the body via the blood. If copper levels in the liver get too high, copper-transporting ATPase 2 leaves the Golgi and transfers copper to small sacs (vesicles) for elimination through bile. Bile is a substance produced by the liver that is important for digestion and the removal of waste products.