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 cy tolysin of Clostridium perfringens type A was crystallized by the vapo r diffusion procedure using polyethyleneglycol 4000 and sodium chlorid e as precipitants in 2-(cyclohexylamino)ethanesulfonic acid (CHES) buf fer at pH 9.5. The diffraction patterns of precession photographs indi cated that the crystals belong to the orthorhombic system and the spac e group C222(1) with unit-cell dimensions of a = 47.7 Angstrom, b = 18 2.0 Angstrom and c = 175.8 Angstrom. Assuming that the asymmetric unit contains one or two molecules (Mw 52 700), the V-m value is calculate d as 3.6 or 1.8 Angstrom(3)/dalton, respectively. The crystals diffrac t X-rays to at least 3 Angstrom resolution and are suitable for high r esolution X-ray crystal structure determination.