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, and functions as a half-transporter to limit intestinal absorption and promote biliary excretion of sterols. Disruption of this gene in mice results in thrombocytopenia, prolonged bleeding times, anemia, leukopenia, infertility, shortened life span and cardiomyopathy. Mice lacking this gene show symptoms of sitosterolemia. [provided by RefSeq, Nov 2015]