Crystallization and diffraction data of 1H-3-hydroxy-4-oxoquinoline 2,4-dioxygenase:: a cofactor-free oxygenase of the α/β-hydrolase family

1H-3-Hydroxy-4-oxoquinoline 2,4-dioxygenase (QDO) from Pseudomonas putida 33/1 catalyses the oxygenolysis of 1H-3-hydroxy-4-oxoquinoline to form N-formylanthranilic acid and carbon monoxide without the aid of cofactors. Both N-terminally His(6)-tagged and native QDO were overexpressed in Escherichia coli and purified by conventional chromatographic procedures. Untagged QDO, but not His(6)-tagged QDO, was crystallized by the vapour-diffusion method, giving hexagonal bipyramid crystals belonging to space group P6(1)22. Selenomethionine-containing native QDO was prepared and crystallized under identical conditions. The unit- cell parameters were a = b = 90.1, c = 168.6 angstrom, alpha = beta = 90, gamma = 120 degrees. Using synchrotron radiation, these crystals diffract to 2.5 angstrom. The expression, purification and crystallization of QDO are reported here.