Transporter for gamma-aminobutyrate (GABA) (PubMed:8951816, PubMed:9677314, PubMed:24142252). Can also transport beta-alanine (PubMed:9677314). Can translocate several open-chain GABA analogs (3-aminobutyrate, 3-aminopropanoate, cis-4-aminobutenoate) across the membrane via counterflow against GABA, but cannot transport muscimol (PubMed:9677314). Functions also as a low-affinity proline importer (PubMed:24142252). 4-aminobutanoate(in) + H(+)(in) = 4-aminobutanoate(out) + H(+)(out) beta-alanine(in) + H(+)(in) = beta-alanine(out) + H(+)(out) Amino-acid degradation; 4-aminobutanoate degradation. Positively regulated by TnrA under conditions of nitrogen limitation (PubMed:8951816). Expression is not significantly induced by GABA (PubMed:8951816). A transposon insertion in this gene eliminates the uptake of GABA and severely inhibits the utilization of GABA as a nitrogen source (PubMed:8951816). Triple deletion of gabP, putP and opuE confers resistance to the proline analog 3,4-dehydro-DL-proline (DHP), abolishes GABA utilization and prevents use of proline as a nitrogen source (PubMed:24142252). The ligand-recognition profile of the B.subtilis GabP was found to differ substantially from that of the highly homologous E.coli GabP. B.subtilis GabP exhibits more stringent requirements than E.coli GabP for substrate recognition and translocation. Belongs to the amino acid-polyamine-organocation (APC) superfamily. Amino acid transporter (AAT) (TC 2.A.3.1) family.