Uptake of 4-hydroxybenzoate (4-HB). Can also transport a variety of aromatic acids with hydroxyl substitutions at the 2-, 3- and 4-positions, such as salicylate, 2,4-dihydroxybenzoate, protocatechuate, 3-hydroxybenzoate, vanillate and gentisate. Homotrimer. Belongs to the major facilitator superfamily. Aromatic acid:H(+) symporter (AAHS) (TC 2.A.1.15) family.