Acts as an anion channel mediating the transport of chloride, sulfate and oxalate ions . Mediates the transport of bromide, iodide, nitrate, gluconate, thiocyanate and bicarbonate ions (By similarity). Its permeability towards bicarbonate is weak and increases when pH is above 7 (By similarity). Mediates thiocyanate transport in retinal pigment epithelium cells (By similarity). Mediates iodide transport in the thyroid gland, playing an important role in the synthesis of thyroid hormones and the maintenance of thyroid function . Although it is an anion channel, according to  and  it has been shown to exhibit chloride-bicarbonate exchanger activity.
Subcellular locations: Basolateral cell membrane, Recycling endosome membrane, Apical cell membrane, Lateral cell membrane
Expressed in the cytoplasm in recycling endosomes of medullary collecting duct cells and in acid-secreting gastric parietal cells. Targeted to the basolateral membrane in hypertonicity and potassium depletion.
Expressed in the thyroid gland (at protein level). Expressed in tonsillar high endothelial venule endothelial cells (HEVEC), placenta and in testis, expressed in a subgroup of basal cells in the epididymal ducts.