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 full transporter is a member of the MRP subfamily which is involved in multi-drug resistance. This protein plays an essential role in the defense against toxic compounds and serves as the major high-affinity transporter of leukotriene C4. The encoded protein may also play an essential role in steroid hormone homeostasis as a transporter for steroid hormones and their metabolites. [provided by RefSeq, Nov 2011]