Purification and characterization of Pseudomonas aeruginosa exotoxin

A trypsin-sensitive, heat-labile exotoxin of Pseudomonas aeruginosa strain P-A-103 has been purified by a procedure that includes membrane ultrafiltration, hydroxylapatite chromatography, ion-exchange cellulose chromatography, and gel filtration chromatography. The procedure resulted in the recovery of 48% of the exotoxin with a 40-fold increase in specific activity (micrograms of protein per median lethal dose [LD(50)]). The mean lethal dose of the purified toxin administered intravenously into mice weighing 20 g was approximately 6 mug of protein. The toxin contained virtually no nucleic acid, detectable pigment, or lipopolysaccharide. When subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis, the toxin separated into at least six protein components which appeared to have similar molecular weights. The estimated molecular weight of the toxin is 54,000, and its isoelectric point is 5.0