High Quality Content by WIKIPEDIA articles! The ATP Binding Cassette Family, also known as the ABC Superfamily is the largest transporter protein family, includes several hundred different membrane transport proteins that utilize the energy of ATP to transport a specific substrate or group of substrates across the cell membrane. These substrates can be ions, sugars, amino acids, phospholipids, cholesterol, peptides, polysaccharides, proteins or other ligands. More than 100 ABC transporters are distributed from prokaryotes to humans. ABC genes are essential for many processes in the cell, and mutations in these genes cause or contribute to several human genetic diseases. 48 ABC genes have been reported in humans. Among these, 16 genes have been determined and 14 of these are related with diseases present in humans such as cystic fibrosis, adrenoleukodystrophy, Stargadt’s disease, drug-resistant tumors, Dubin-Johnson syndrome, Byler’s disease, progressive familiar intrahepatic cholestasis, X-linked sideroblastic anemia, ataxia, and persistent and hyperinsulimenic hypoglycemia in children. ABC transporters are also involved in multiple drug resistance, and this is how some of them were first identified. When the ABC transporter proteins are overexpressed in cancer cells they can export anticancer drugs and render tumors resistant.