Amino acid-proton symporter. Transporter with a broad specificity for histidine, lysine, glutamic acid, alanine, serine, proline and glycine. Involved in both apoplastic transport of amino acids in leaves and their uptake by roots. Inhibited by carbonlycyanide m-chlorophenylhydrazone (CCCP) and DEPC. Expressed in roots, stems, flowers, leaves, siliques and pollen. Found in the tips of roots and in the rhizodermis of emerging roots and in lateral roots. Higher expression in older leaves as compared to joung leaves. Detected first at the hydathodes, then in the epidermis and finally in matures leaves in all mesophyll cells. Not detected in vascular bundles or in seeds. By amino acids. Lower biomass at the time of harvest, but no visible phenotype until bolting. Decreased uptake of L-histidine, L-glutamine, glutamic acid, L-serine, glycine, L-asparagine, aspartic acid, L-proline and L- or D-alanine. Belongs to the amino acid/polyamine transporter 2 family. Amino acid/auxin permease (AAAP) (TC 2.A.18.2) subfamily. PubMed:9390441 shows a high affinity for lysine while PubMed:16816136 and PubMed:17293438 found no significant transport of this amino acid.