- Crystal structures of wild-type p-hydroxybenzoate hydroxylase complexed with 4-aminobenzoate,2,4-dihydroxybenzoate, and 2-hydroxy-4-aminobenzoate and of the Tyr222Ala mutant complexed with 2-hydroxy-4-aminobenzoate. Evidence for a proton channel and a new binding mode of the flavin ring. Schreuder, H.A., Mattevi, A., Obmolova, G., Kalk, K.H., Hol, W.G., van der Bolt, F.J., van Berkel, W.J. Biochemistry (1994)