Crystallization of the protective antigen protein of Bacillus anthracis

The protective antigen protein, one of the three separate proteins constituting the exotoxin system of Bacillus anthracis, has been crystallized in a form suitable for structural studies. The crystal form which is most amenable to x-ray analysis is orthorhombic, space group P2(1)2(1)2(1), a = 101.1 A, b = 95.4 A, c = 87.3 A, with one protective antigen monomer/asymmetric unit. The crystals diffract to approximately 3.0-A resolution.