Crystallization and some properties of leukocidin from Pseudomonas aeruginosa

A leukocidin was isolated and purified from autolysates of Pseudomonas aeruginosa strain 158 by a combination of procedures such as column chromatography on DEAE-Sephadex A-50, gel filtration on Sephadex G-100, and zone electrophoresis on pevikon. The purified preparation showed a single band in each experiment using electrophoreses in the presence or absence of sodium dodecyl sulfate (SDS), and the agar-gel Ouchterlony immunodiffusion test. The purified pseudomonal leukocidin was crystallized by salting out with saturated ammonium sulfate at pH 7.0 in a needle-leaf like form. The molecular weight of the leukocidin was estimated to be 42,500 by SDS-polyacrylamide gel electrophoresis, 40,000 by gel filtration, and 44,700 (3.3 S20,W) by sucrose density gradient centrifugation. The isoelectric point of the leukocidin was estimated to be at pH 6.3 by isoelectrofocusing. Morphological studies of a leukocidin-treated leukocyte showed that the formation of vacuoles of cytosolic granules and the swelling of the lobulated nuclei occurred prior to leukocyte enlargement. In a slide adhesion test with rabbit polymorphonuclear leukocytes (1 X 10(6], the minimum cytotoxic dose for the destruction of all leukocytes was 13-20 ng of the crystallized toxin. Rabbit lymphocytes were one-thirtieth as sensitive as rabbit leukocytes. Leukocidin did not act on rabbit erythrocytes or on platelets.