[Band 3 protein, anion exchange protein of the erythrocyte membrane]

Band 3 protein is the major transmembrane protein of the erythrocyte membrane, comprising 25% of the total membrane protein and existing at 10(6) copies per cell, and mediates the rapid exchange of anions across the membrane. The exchange of Cl- for HCO3- anions plays an important role on the regulation of oxygen and bicarbonate delivary to or from peripheral tissues. Band 3 protein has functionally distinct two domains. The membrane-spanning domain, 55K domain, is believed to span the membrane bilayer 14 times and mediates the rapid anion exchange. The complementary cytosolic domain, 40K domain, is an anchor for the cytoskeletal proteins and regulates the cell deformability and the cell life span. The purpose of this paper is to review the physiological functions of band 3 protein and the anion exchange mechanisms.