Amino-acid permease with rather broad substrate specificity (PubMed:21764911). Transports many amino acids including proline, methionine, leucine, valine, isoleucine, phenylalanine, tryptophan, threonine and tyrosine, but not basic ones (arginine) and citrulline (PubMed:21764911, PubMed:28028545). Functions as a sensor via detection of some amino acids including methionine, leading to a rapid activation of trehalase, a downstream target of PKA (PubMed:21764911). Expression is under control of the CSY1 amino-acid sensor (PubMed:28028545). Expression is also regulated by PLC1 and GCN4 (PubMed:16207920, PubMed:16215176). Expression is induced during development of rat catheter biofilm (PubMed:19527170). Belongs to the amino acid-polyamine-organocation (APC) superfamily. YAT (TC 2.A.3.10) family.