Crystallization and preliminary X-ray diffraction studies of theta-toxin (perfringolysin O), a pore-forming cytolysin of Clostridium perfringens

theta-Toxin (perfringolysin O), a cholesterol-binding, pore-forming cytolysin of Clostridium perfringens type A was crystallized by the vapor diffusion procedure using polyethyleneglycol 4000 and sodium chloride as precipitants in 2-(cyclohexylamino)ethanesulfonic acid (CHES) buffer at pH 9.5. The diffraction patterns of precession photographs indicated that the crystals belong to the orthorhombic system and the space group C222(1) with unit-cell dimensions of a = 47.7 Angstrom, b = 182.0 Angstrom and c = 175.8 Angstrom. Assuming that the asymmetric unit contains one or two molecules (Mw 52 700), the V-m value is calculated as 3.6 or 1.8 Angstrom(3)/dalton, respectively. The crystals diffract X-rays to at least 3 Angstrom resolution and are suitable for high resolution X-ray crystal structure determination.