Cloning, overexpression, crystallization and preliminary X-ray analysis of a family 1 β-glucosidase from Streptomyces

An intracellular β-glucosidase (Bg13) from Streptomyces sp. has been cloned and overexpressed in Escherichia coli. The introduction of a His tag at the N-terminal end of the protein has allowed its purification to homogeneity by a single chromatographic step, with yields of 150-200 mg of pure protein per litre of E. coli culture. The enzyme (52.6 kDa) is a retaining glycosidase able to hydrolyze a wide range of disaccharides and oligosaccharides and to perform transglycosylation. Crystals of recombinant Bg13 have been grown from an ammonium sulfate solution using the hanging-drop vapour-diffusion method at 293 K. The crystals belong to the orthorhombic space group 1222 with unit-cell dimensions a = 101.6, b = 113.4 and c = 187.5 Å at room temperature and contain two molecules per asymmetric unit. A full 1.69 Å resolution diffraction data set (97.7% completeness) has been collected from frozen crystals in a solution containing 30% sucrose, using synchrotron radiation.