Mediates sodium- and bicarbonate-dependent electrogenic sodium bicarbonate cotransport, with a Na(+):HCO3(-) stoichiometry of 2:1. May have a housekeeping function in regulating the pH of tissues in which it is expressed. May play a role in mediating Na(+):HCO3(-) cotransport in hepatocytes and intrahepatic cholangiocytes. May also be important in protecting the renal paranchyma from alterations in urine pH. Localized predominantly to the basolateral sinusoidal membrane in hepatocytes. Observed in hepatocytes and in the apical region of bile duct intrahepatic cholangiocytes of liver. Also observed in uroepithelium cells lining the outer pelvic wall of the kidney (at protein level). Highly expressed in colon, distal colon, liver, kidney and testis. Moderate expression in duodenum and stomach and weak expression in heart. In kidney, very weakly expressed in the inner medulla, but abundantly expressed in cortex and outer medulla in the medullary thick ascending and cortical thick ascending limbs of the loop of Henle. Belongs to the anion exchanger (TC 2.A.31) family.