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 (By similarity). Belongs to the major facilitator superfamily. Aromatic acid:H(+) symporter (AAHS) (TC 2.A.1.15) family.