ATP-binding cassette sub-family G member 1 is a protein that in humans is encoded by the ABCG1 gene. It is a homolog of the well-known Drosophila gene white. 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 is involved in macrophage, cholesterol and phospholipids transport, and may regulate cellular lipid homeostasis in other cell types.