Purification, crystallization and preliminary X-ray crystallographic study of α-amylase from Bacillus stearothermophilus

A recombinant alpha-amylase from Bacillus stearothermophilus was found to be produced as several isoforms arising from different N-terminal processing. Some of those isoforms were purified to homogeneity and crystallized at 293 K using the hanging-drop vapour-diffusion method under the following conditions: 35 mM sodium acetate (pH 4.6), 6.25% (nu/nu) 2-propanol, in the presence of 1.23% (w/nu) acarbose (a pseudo-oligosaccharide inhibitor) in the drop. The crystals diffracted beyond 2.0 Angstrom resolution using synchrotron radiation at the Photon Factory, Tsukuba. They belong to the monoclinic space group P2(1), with unit-cell parameters a = 53.7 (2), b = 92.9 (4), c = 53.2 (2) Angstrom, beta = 109.4 (1)degrees.