The membrane-associated protein encoded by this gene is a member of the superfamily of ATP-binding cassette (ABC) transporters. ABC proteins transport various molecules across extra- and intra-cellular membranes. ABC genes are divided into seven distinct subfamilies (ABC1, MDR/TAP, MRP, ALD, OABP, GCN20, White). This protein is a member of the MRP subfamily which is involved in multi-drug resistance. This protein functions in the canalicular surface of the hepatocyte and in biliary transport, and appears to contribute to drug resistance in mammalian cells. Several different mutations in the human gene have been observed in patients with Dubin-Johnson syndrome (DJS), an autosomal recessive disorder characterized by conjugated hyperbilirubinemia. Alternative splice variants have been observed for this gene; however, they have not been fully described. [provided by RefSeq, Jul 2008]