Large-scale purification and characterization of the exotoxin of Pseudomonas aeruginosa

The exotoxin (PE) of Pseudomonas aeruginosa was purified from 50-liter cultures by a simple three-step procedure, yielding 135 mg of essentially homogeneous protein. In Ouchterlony gel diffusion, PE produces a single line which does not interact with a diphtheria toxin-antitoxin precipitin line. The protein has a molecular weight of 66,000, an isoelectric point of 5.1, N-terminal arginine, and four disulfide bridges. The amino acid composition shows no apparent similarity to that of diphtheria toxin. The median lethal dose of this PE preparation in mice weighing 20 g is 0.1 mug. The median lethal dose in 350-g rats is 20 mug. The cytotoxicity of PE for mouse L929 fibroblasts is completely neutralized by small amounts of specific pony antitoxin. The exotoxin possesses adenosine diphosphate-ribosylation activity. Both cytotoxic and adenosine diphosphate-ribosylation activities are shown to be properties of the intact 66,000-dalton protein.