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. Activity is inhibited by 4,4'-di-isothiocyanatostilbene-2,2'-disulfonic acid (DIDS - an inhibitor of several anion channels and transporters). Expressed in the apical plasma membrane domain of a subset of collecting ducts in the renal medulla. Highest expression observed in liver, spleen and testis; moderate expression in the choroid plexus, hippocampus, cerebrum and cerebellum of brain, and in kidney cortex and kidney medulla. Also observed in heart, pancreas, muscle, lung, placenta, stomach and small intestine. Weakest expression seen in peripheral blood lymphocytes, colon, duodenum, jejunum, ileum and skeletal muscle. Incomplete sequence. Belongs to the anion exchanger (TC 2.A.31) family.