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. May have a higher activity than isoform 1. Inhibited by stilbene derivatives and regulated by cyclic AMP. Homodimer. Interacts with CA2/carbonic anhydrase 2 and CA4/carbonic anhydrase 4 which may regulate transporter activity. Isoform 1 but not isoform 2 interacts with AHCYL1 (via PEST domain when phosphorylated); the interaction increases SLC4A4 isoform 1 activity. Interacts with AHCYL2. Expressed in colonic mucosa, kidney cortex and to gastric mucosa. Phosphorylation of Ser-1026 by PKA increases the binding of CA2 and changes the Na(+):HCO3(-) stoichiometry of the transporter from 3:1 to 2:1. Phosphorylated in presence of STK39 and dephosphorylated in presence of PP1 phosphatase; phosphorylation seems to inhibit SLC4A4 activity. N-glycosylated. May not be necessary for the transporter basic functions. Belongs to the anion exchanger (TC 2.A.31) family.