ABC Transporters (ATP-binding cassette transporters, 9q22-q31)

ABC transporters constitute a large family of proteins, which hydrolyze ATP and mediate transfers through membranes. Altogether 56 ABC transporter genes are known and 38 of them are present in all vertebrates. These are now often called TAP. The ABC transporters have two membrane-spanning (MSD) and the dimeric ATP-nucleotide binding domains (NBD). MSDs may show greater variations, depending whether they operate as a pump or a conductance channel. The NBD subunits play the role of the engines of the transport and interact through their arm 1 with the two MSDs. The ABCA4/ABCR mutations may account for Stargardt disease (STGD1), fundus flavimaculatus (FFM, retinitis pigmentosa (RP) and cone-rod dystrophy (CRD), all recessive with somewhat overlapping retinal symptoms. ABC transporters may affect adrenoleukodystrophy, cystic fibrosis, retinal degeneration, hypercholesterolemia and cholestasis (see Fig. A2). By 2001, 48 ABC transporters belonging to 7 gene families have been identified. TAP...