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 (C 1 ) component and a larger oxygenase (C 2 ) component. The C 1 component supplies a reduced flavin in its free form to the C 2 counterpart for hydroxylation. In addition, HPA can bind to C 1 and enhance the flavin‐reduction rate without becoming hydroxylated. The recombinant C 1 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 P 2 1 2 1 2 1 , with unit‐cell parameters a = 47.78, b = 59.92, c = 211.85 Å, and contained two molecules of C 1 per asymmetric unit.