Involved in the uptake of ammonium/ammonia (NH(4)(+)/NH(3)) (PubMed:22804733, PubMed:24958855). Transport is electrogenic (PubMed:22804733, PubMed:24958855). Transport the ammonium and methylammonium cation with high specificity (PubMed:24958855). Transport is pH-dependent, with a steep decline at pH values about 5.0. Homotrimer. Belongs to the ammonia transporter channel (TC 1.A.11.2) family.