The LAN blood group system consists of one antigen carried on a multipass membrane protein (a.k.a. ATP-binding cassette, sub- family B, member 6 [ABCB6]) of 842 amino acids. ABCB6 is an ATP-dependent transporter of porphyrins (including heme) and is localized in the golgi apparatus, lysosomes, and plasma membranes. The biologically active protein is a homodimer. ABCB6 is up regulated during erythroid maturation.