Functions as an electroneutral and bidirectional ammonium transporter. May regulate transepithelial ammonia secretion (By similarity). Homotrimer. Also detected at the basolateral membrane and in subapical vesicles. Chronic acidosis induces relocalization to the apical cell membrane. Expressed by connecting tubule cells and intercalated cells of the collecting duct in kidney (at protein level). N-glycosylated. Belongs to the ammonium transporter (TC 2.A.49) family. Rh subfamily.