Low affinity ammonium transporter of the plasma membrane (PubMed:24707045). May be involved in drug resistance through pumping them out of the cell (By similarity). Expression is induced by neocarzinostatin (PubMed:11562456). Expression is induced during G2 phase of cell cycle (PubMed:16278933). Expression is slightly up-regulated upon exposure to boric acid (PubMed:19414602). The AMF1 promoter contains 8 predicted enhancer box (E-box) transcription factor binding domains (PubMed:24707045). Does not affect boron tolerance (PubMed:19414602). Impairs methylammonium (MA) transport and toxicity (PubMed:24707045). Belongs to the major facilitator superfamily.