The 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 White subfamily. In humans, this protein functions as a half-transporter to limit intestinal absorption and promote biliary excretion of sterols; however, the function of the mouse gene has not been determined. Mutations in the human gene have been associated with sterol accumulation, atheroschlerosis, and sitosterolemia. [provided by RefSeq, Jul 2008]