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 MDR/TAP subfamily. Members of the MDR/TAP subfamily are involved in multidrug resistance. This gene encodes a membrane glycoprotein which confers a multidrug-resistance phenotype. The protein encoded by the human gene is an ATP-dependent drug efflux pump for xenobiotic compounds which is responsible for decreased drug accumulation in multidrug-resistant cells and mediates the development of resistance to anticancer drugs. [provided by RefSeq, Jul 2008]