The function of BEST4 (bestrophin 4, ENSG00000142959) is as follows. Ligand-gated anion channel that allows the movement of anions across cell membranes when activated by Calcium (Ca2+) (PubMed:12907679, PubMed:18400985). Mediates the movement of hydrogencarbonate and chloride (PubMed:12907679, PubMed:18400985). .