Crystallization and preliminary X-ray analysis of the reductase component of p-hydroxyphenylacetate 3-hydroxylase from Acinetobacter baumannii

p-Hydroxyphenylacetate 3-hydroxylase (HPAH) from Acinetobacter baumannii catalyzes the hydroxylation of p-hydroxyphenylacetate (HPA) at the ortho position to yield 3,4-dihydroxyphenylacetate (DHPA). HPAH from A. baumannii is a two-component flavoprotein consisting of a smaller reductase (C₁) component and a larger oxygenase (C₂) component. The C₁ component supplies a reduced flavin in its free form to the C₂ counterpart for hydroxylation. In addition, HPA can bind to C₁ and enhance the flavin-reduction rate without becoming hydroxylated. The recombinant C₁ component was purified and crystallized using the microbatch method at 295 K. X-ray diffraction data were collected to 2.3 Å resolution using synchrotron radiation on the BL13B1 beamline at NSRRC, Taiwan. The crystal belonged to the orthorhombic space group P2₁2₁2₁, with unit-cell parameters a = 47.78, b = 59.92, c = 211.85 Å, and contained two molecules of C₁ per asymmetric unit.