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. It lacks several highly conserved residues found in other ATP-binding proteins; this suggests that this protein may not bind ATP and may require dimerization with another subunit to form a functional ATP-transporter. The function of this gene has not yet been determined; however, high levels of expression in the thymus and spleen suggest a potential role in the transport of specific peptides or hydrophobic compounds from lymphocytes. [provided by RefSeq, Jul 2008]