Crystallization and preliminary X-ray crystallographic analysis of BxlA, an intracellular β-D-xylosidase from Streptomyces thermoviolaceus OPC-520

BxlA from Streptomyces thermoviolaceus OPC-520, together with the extracellular BxlE and the integral membrane proteins BxlF and BxlG, constitutes a xylanolytic system that participates in the intracellular transport of xylan-degradation products and the production of xylose. To elucidate the mechanism of the hydrolytic degradation of xylooligosaccharides to xylose at the atomic level, X-ray structural analysis of BxlA was attempted. The recombinant BxlA protein (molecular weight 82 kDa) was crystallized by the hanging-drop vapour-diffusion method at 289 K. The crystals belonged to the monoclinic space group C2, with unit-cell parameters a = 142.2, b = 129.5, c = 101.4 angstrom, beta = 119.8 degrees, and contained two molecules per asymmetric unit (V-M = 2.47 angstrom(3) Da(-1)). Diffraction data were collected to a resolution to 2.50 angstrom and provided a data set with an overall Rmerge of 8.3%.