Crystallization and preliminary X-ray diffraction studies of a ferredoxin reductase component of carbazole 1,9a-dioxygenase from Novosphingobium sp KA1

Carbazole 1,9a-dioxygenase (CARDO) is the initial enzyme of the carbazole-degradation pathway. The CARDO of Novosphingobium sp. KA1 consists of a terminal oxygenase, a putidaredoxin-type ferredoxin and a ferredoxin-NADH oxidoreductase (Red) and is classified as a class IIA Rieske oxygenase. Red from KA1 was crystallized at 278 K by the hanging-drop vapour-diffusion method using PEG 4000. The crystal diffracted to 1.58 angstrom resolution and belonged to space group P3(2), with unit-cell parameters a = b = 92.2, c = 78.6 angstrom, alpha = gamma = 90, beta = 120 degrees. Preliminary analysis of the X-ray diffraction data revealed that the asymmetric unit contained two Red monomers. The crystal appeared to be a merohedral twin, with a twin fraction of 0.32 and twin law (-h, -k, l).