“…The pTrcHisA plasmids encoding native perfringolysin (Department of Microbiology and Immunology, College of Medicine, University of Oklahoma, USA) were transformed in chemically competent E. coli TunerTM(DE3)pLysS cells (Novagen, Darmstadt, Germany). The proteins were expressed in Terrific Broth (24% Tryptone (Oxoid, Hampshire, UK), 42% Yeast extract (BD), 4% glycerol, 0.72 M Na 2 HPO 4 , 0.16 M NaH 2 PO 4 ) and the protein expression was induced with 0.5 mM isopropyl β- d -thiogalactopyranoside (IPTG, Promega, Madison, WI, USA) [ 22 ]. The E. coli cells were lysed by sonication in a lysis buffer (pH 7.4) containing 20 mM NaPO 4 , 0.5 M NaCl, 20 mM Imidazole, 1 mg/mL lysozyme (Sigma-Aldrich, St. Louis, MO, USA) supplemented with protease-inhibitor cocktail (Sigma-Aldrich, St. Louis, MO, USA).…”