Purification, crystallization and crystallographic analysis of Dictyostelium discoideum phenylalanine hydroxylase in complex with dihydrobiopterin and FeIII.

Dictyostelium discoideum phenylalanine hydroxylase (DicPAH; residues 1-415) was expressed in Escherichia coli and purified for structural analysis. Apo DicPAH and DicPAH complexed with dihydrobiopterin (BH(2)) and Fe(III) were crystallized using 0.06 M PIPES pH 7.0, 26%(w/v) PEG 2000 by the hanging-drop vapour-diffusion method. Crystals of apo DicPAH and the DicPAH-BH(2)-Fe(III) complex diffracted to 2.6 and 2.07 A resolution, respectively, and belonged to space group P2(1), with unit-cell parameters a = 70.02, b = 85.43, c = 74.86 A, beta = 110.12 degrees and a = 70.97, b = 85.33, c = 74.89 A, beta = 110.23 degrees , respectively. There were two molecules in the asymmetric unit. The structure of DicPAH has been solved by molecular replacement.