Electrogenic sodium/bicarbonate cotransporter with a Na(+):HCO3(-) stoichiometry varying from 1:2 to 1:3. May regulate bicarbonate influx/efflux at the basolateral membrane of cells and regulate intracellular pH. Homodimer. Expressed in kidney and to a lower extent in bladder, brain, intestine, large intestine and eye. Belongs to the anion exchanger (TC 2.A.31) family.