Involved in glutaminase-dependent acid resistance. Exchanges extracellular glutamate (Glu) for intracellular gamma-aminobutyric acid (GABA) under acidic conditions. The ability to survive the extremely acidic conditions of the stomach is essential for successful colonization of the host by commensal and pathogenic bacteria. 4-aminobutanoate(in) + L-glutamate(out) = 4-aminobutanoate(out) + L-glutamate(in) Shows pH-dependent activity (By similarity). The glutamate analog L-trans-pyrrolidine-2,4-dicarboxylic acid (L-PDC) blocks the uptake of glutamate by selective inhibition (PubMed:12855178). Belongs to the amino acid-polyamine-organocation (APC) superfamily. Glutamate:GABA antiporter (GGA) (TC 2.A.3.7) family.