Purification, crystallization and preliminary X-ray analysis of a hexameric beta-glucosidase from wheat

Abstract

The wheat beta-glucosidase TaGlu1b, which is only active in a hexameric form, was tagged with 6xHis at the N-terminus, overexpressed in Escherichia coli and purified in two steps. The protein complexed with a substrate aglycone was crystallized at 293 K from a solution containing 10 mM HEPES pH 7.2, 1 M LiSO4 and 150 mM NaCl using the hanging-drop vapour-diffusion method. Diffraction data were collected to 1.7 A at the Photon Factory. The crystal belongs to space group P4(1)32, with unit-cell parameters a = b = c = 194.65 A, alpha = beta = gamma = 90 degrees. The asymmetric unit was confirmed by molecular-replacement solution to contain one monomer, giving a solvent content of 72.1%.

Figure 1

Crystals of TaGlu1b obtained using 10 mM HEPES pH 7.2, 1 M LiSO₄, 150 mM NaCl. These crystals appeared in one week at 293 K and have a maximum size of 0.3 mm along one dimension.

Figure 2

A representative diffraction image of a crystal of TaGlu1b complexed with DIMBOA collected on beamline BL6A at the Photon Factory using an ADSC Quantum 4 detector. The box in the left image indicates the position of the image magnified on the right.