Transports 4-hydroxybenzoate (4-HBA) and protocatechuate across the membrane. Driven by the proton motive force. Functions also as a chemoreceptor, which is required for chemotaxis to aromatic acids. Amino acids located between the second and third, and the eighth and ninth transmembrane regions are required for substrate transport. Belongs to the major facilitator superfamily. Aromatic acid:H(+) symporter (AAHS) (TC 2.A.1.15) family.