Transports methylammonium or ammonium in yeast cells, preferentially at high medium pH. May participate in vacuolar compartmentation and detoxification of ammonium. Interacts with cucumber mosaic virus (CMV) Protein 1a. Tonoplast. Widely expressed. By ammonium nitrate in roots. Expressed in roots with a circadian rhythm showing an increase after onset of light, a peak approximately at midday and a decline to lowest levels before offset of light. Aquaporins contain two tandem repeats each containing three membrane-spanning domains and a pore-forming loop with the signature motif Asn-Pro-Ala (NPA). Belongs to the MIP/aquaporin (TC 1.A.8) family. TIP (TC 1.A.8.10) subfamily.