Family 2.A.31 - The Anion Exchanger Family       

Family ID: 52640

Characterized protein members of the AE family are found only in animals. Uncharacterized AE homologues are found in yeast and plants, and possibly also in bacteria. The animal AE proteins consist of homodimeric complexes of integral membrane proteins that vary in size from about 900 amino acyl residues to about 1250 residues. Their N-terminal hydrophilic domains may interact with cytoskeletal proteins and therefore play a cell structural role. The membrane-embedded C-terminal domains may each span the membrane 14 times as a-helices. They preferentially catalyze anion exchange (antiport) reactions. There are three known paralogous isoforms of anion exhangers (AE1, AE2 and AE3) in mammals such as mice and rats. The different isoforms have different tissue distributions.

AE1 in human red blood cells has been shown to transport a variety of inorganic and organic anions. Divalent anions may be symported with H+. Additionally, it catalyzes flipping of several anionic amphipathic molecules such as sodium dodecyl sulfate (SDS) and phosphatidic acid from one monolayer of the phospholipid bilayer to the other monolayer. The rate of flipping is sufficiently rapid to suggest that this AE1-catalyzed process is physiologically important in red blood cells and possibly in other animal tissues as well. Anionic phospholipids and fatty acids are likely to be natural substrates.