Crystallization and preliminary X-ray crystallographic analysis of BxlE, a xylobiose transporter from Streptomyces thermoviolaceus OPC-520.

Together with the integral membrane proteins BxlF and BxlG, BxlE isolated from Streptomyces thermoviolaceus OPC-520 forms an ATP-binding cassette (ABC) transport system that mediates the uptake of xylan. To clarify the structural basis of sugar binding by BxlE at the atomic level, recombinant BxlE was crystallized using the hanging-drop vapour-diffusion method at 290 K. The crystals belonged to the monoclinic space group P2(1), with unit-cell parameters a = 44.63, b = 63.27, c = 66.40 A, beta = 103.05 degrees, and contained one 48 kDa molecule per asymmetric unit (V(M) = 1.96 A3 Da(-1)). Diffraction data collected to a resolution of 1.65 A using a rotating-anode X-ray source gave a data set with an overall R(merge) of 2.6% and a completeness of 91.3%. A data set from a platinum derivative is being used for phasing by the SAD method.