Catalysis of the reaction: 4-hydroxybenzoate + 5-phospho-alpha-D-ribose 1-diphosphate + H+ = 4-(beta-D-ribofuranosyl)phenol 5'-phosphate + CO2 + diphosphate. Both 4-hydroxybenzoate and 4-aminobenzoate may be used as substrates, but only the former is known to be produced by methanogenic archaea.
beta-RFAP synthase activity