Crystallization and preliminary X-ray analysis of α-xylosidase from Escherichia coli

Glycoside hydrolases have been implicated in many biological processes. To date, they have been classified into 93 glycoside hydrolase (GH) families based on amino-acid sequence similarity. alpha-Xylosidase from Escherichia coli belongs to GH family 31 and catalyzes the release of alpha-xylose from the non-reducing terminal side of alpha-xyloside. Single crystals of alpha-xylosidase have been grown by vapour diffusion at 293 K from 10%( w/v) PEG 20 K, 2%(v/v) 2-propanol, 2% (v/v) glycerol and 0.1 M 2-morpholinoethanesulfonic acid pH 5.5. These crystals belong to space group P2(1)2(1)2(1) and X-ray diffraction data were collected to a resolution of 2.75 angstrom. Crystals of selenomethionyl-substituted alpha-xylosidase were also obtained, which diffracted to at least 3.0 angstrom. Based on the value of V-M, the asymmetric unit in these crystals was assumed to contain six molecules.