CD233
CD233 is erythroid band 3, the anion exchanger 1 (AE1) encoded by SLC4A1 and the most abundant integral protein of the erythrocyte membrane. The protein catalyzes electroneutral exchange of chloride and bicarbonate across the membrane, enabling the chloride shift that supports tissue CO2 transport and pulmonary CO2 release. Its cytoplasmic N-terminal domain binds ankyrin, protein 4.2, denatured hemoglobin, and glycolytic enzymes, anchoring the spectrin skeleton and organizing red cell metabolism. CD233 carries the Diego blood group system antigens. Mutations in SLC4A1 produce hereditary spherocytosis and hereditary stomatocytosis in Western populations, while the Southeast Asian ovalocytosis deletion confers resistance to severe malaria.
