High affinity ammonium transporter probably involved in ammonium uptake from the soil, long-distance transport to the shoots and re-uptake of apoplastic ammonium that derives from photorespiration in shoots. Contributes with AMT1-3 to the overall ammonium uptake capacity in roots under nitrogen-deficiency conditions. Measured in yeast knockout mutant YCW012. Self interacts. Interacts with the receptor protein kinases CEPR2, At2g28990 and PAM74. Highly expressed in roots. Expressed in root tips, root hairs, root epidermis, rhizodermis, cortex and pericycle. Expressed in leaves epidermal and mesophyll cells. By nitrogen deprivation in roots and nitrogen supply in leaves. No effect on ammonium uptake. Higher expression of AMT1-2; AMT1-3 and AMT2-1. Belongs to the ammonia transporter channel (TC 1.A.11.2) family.