Crystallization and preliminary X-ray crystallographic analysis of α-amylase from Bacillus subtilis

Large crystals of α-amylaae from Bacillus subtilis have been obtained at room temperature using polyethylene glycol 6000 as precipitant. They grow to typical dimensions of 0.25 mm × 0.3 mm × 2.0 mm in five days. The crystals belong to the orthorhombic space group P2₁2₁2₁, with unit cell dimensions of a = 85.46 Å, b = 166.5 Å and c = 332.7 Å. The asymmetric unit seems to contain eight molecules of α-amylase, with crystal volume per protein mass (V_m) of 2.69 ų/Da and solvent content of 54.3% by volume. Despite a very long c-axis, the crystals diffracted to about 2.2 Å Bragg spacing using the rotating anode X-rays and were resistant to damage by X-rays. Thus they are suitable for structure determination by X-ray methods at high resolution. X-ray diffraction data have been collected to 3.4 Å Bragg spacing from a native crystal.