2.A.31.1.4
Anion exchanger 1 (AE1, Band 3 anion exchanger, Slc4a1) of 918 aas and 13 TMSs in a 1 + 12 TMS arrangement that looks like a 1 + 6 + 6 arrangement.  The protein functions both as a transporter that mediates electroneutral inorganic anion exchange (e.g., Cl^- against HCO₃^-) across the cell membrane and as a structural protein. It is a major integral membrane glycoprotein of the erythrocyte membrane required for normal flexibility and stability of the erythrocyte membrane and for normal erythrocyte shape via the interactions of its N-terminal cytoplasmic domain with cytoskeletal proteins, glycolytic enzymes, and hemoglobin. It mediates chloride-bicarbonate exchange in the kidney, and is required for normal acidification of the urine. A mutant containing the sole C462 can drive a marginal Cl^- current, but the minimal configuration necessary to get optimal functional expression includes residues C462, C583 and C588 (Martial et al. 2007). Trout AE1 can function both as a antiporter or a channel, and mutations affecting one or the other function or both have been isolated (Martial et al. 2006).