Crystallization and preliminary crystallographic study of bacterial alpha-amylases

Crystallization of bacterial alpha-amylases has been achieved by the hanging-drop vapor diffusion method. The crystals of Bacillus licheniformis and B. licheniformis 584 amylases are isomorphous to each other. The crystals of B. licheniformis amylase belong to the tetragonal system, space group P4(2)2(1)2 with cell dimensions of a = 119.3 and c = 85.4 A. The asymmetric unit contains one molecule of amylase, with a volume per molecular mass, Vm, of 2.75 A3/Da. The crystals of B. licheniformis and B. licheniformis 584 amylases diffract beyond 2.5 A resolution and are suitable for X-ray diffraction analysis. The crystals of B. amyloliquefaciens amylase are orthorhombic, and have space group C222(1), with cell dimensions of a = 154, b = 298, and c = 90 A. The asymmetric unit contains three to five molecules. In the crystallization of B. licheniformis and B. licheniformis 584 amylases, the addition of EDTA was indispensable to obtain large single crystals, while it had an adverse effect on the crystallization of B. amyloliquefaciens amylase, producing a large amount of small crystals.