Crystallization and preliminary X-ray diffraction studies of a-toxin from two different strains (NCTC8237 and CER89L43) of Clostridium perfringens

The alpha-toxin of Clostridium perfringens is the major virulence determina nt for gas gangrene in man. The gene encoding the alpha-toxin has been clon ed into E. coli from two strains of the bacterium (NCTC8237 and CER89L43) a nd subsequently purified to homogeneity. The two strains of alpha-toxin dif fer by five amino acids, resulting in the toxin from NCTC8237 being sensiti ve to chymotrypsin digestion while that from CER89L43 is resistant. The alp ha-toxin from each of these strains has been crystallized in two different forms by the hanging-drop vapour-diffusion method at 293 K. CER89L43 form I crystals belong to space group R32 and have two molecules in the crystallo graphic asymmetric unit and a unit cell with a = b = 151.4, c = 195.5 Angst rom, alpha = beta = 90, gamma = 120 degrees. The crystals diffracted to d(m in) = 1.90 Angstrom. The characteristics of the NCTC8237 form I crystals ha ve already been reported. The form II crystals from both strains belong to space group C222(1) with one molecule in the crystallographic asymmetric un it and, for strain CER89L43, have cell dimensions a = 61.05, b = 177.50, c = 79.05 Angstrom, alpha = beta = gamma = 90 degrees, while for strain NCTC8 237 the cell dimensions are a = 60.50, b = 175.70, c = 80.20 Angstrom, alph a = beta = gamma = 90 degrees. The crystals diffracted to maximum resolutio ns of 1.85 and 2.1 Angstrom for the CER89L43 and the NCTTC8237 strains, res pectively.