| Modification Notes |
ATP-binding cassette (ABC) transporters are an evolutionarily conserved family of proteins that catalyze the transport of molecules across extra- and intracellular membranes through the energy of ATP hydrolysis. The ABC gene family comprises seven subfamilies, ABC1, MDR/TAP, MRP, ALD, OABP, GCN20 and White. ABC proteins are either full molecules, with two nucleotide-binding folds (NBFs) and two sets of transmembrane domains (TMs), or half molecules, with one NBF and one set of TM domains. ABCG4, as well as all other half transporters, forms either a hetero- or homodimer in order to mediate transport function. A 646 amino acid protein, ABCG4 is important in macrophage lipid homeostasis, with the highest expression detected in brain, thymus, spleen and heart. The gene encoding for the ABCG4 protein maps to chromosome 11q23.3, a locus which includes several other genes involved in cholesterol and lipid metabolism. This locus also includes the locus for primary hypoalphalipoproteinemia. |