Purification of dermonecrotic toxin from a sonic extract of Pasteurella multocida SP-72 serotype D

A procedure was developed to purify dermonecrotic toxin (DNT) from a sonic extract of a serotype D strain of Pasteurella multocida. Sonic extract containing DNT was applied to a DEAE-Sephacel column and eluted by a linear gradient of NaCl. Upon rechromatographing, fractions with dermonecrotic activity for guinea pigs were applied on a second Sephacel column, and a pooled fraction with the toxic activity was filtered through a Sephadex G-200 column. Pooled fractions with the toxic activity were subjected to polyacrylamide disc gel electrophoresis (PAGE), and the toxic substance was eluted from each sliced gel. Eluted fractions with the toxic activity were rechromatographed on a second Sephadex G-200 column, and a pooled fraction with high dermonecrotic activity was referred to as a purified DNT. The activity of purified DNT was increased by 1,000 times, and the average yield was about 1.8%. The purified DNT was homogeneous as determined by Ouchterlony double immunodiffusion, crossed immunoelectrophoresis, and thin-layer isoelectric focusing in polyacrylamide gels and gave a single band on PAGE and sodium dodecyl sulfate-PAGE. The molecular weight of the toxin was ca. 160,000 as determined by sodium dodecyl sulfate-PAGE. The isoelectric point of the toxin was ca. 4.7 to 4.8. Amino acid analysis of the purified DNT revealed that the toxin was composed of characteristically high proportions of glutamic acid, aspartic acid, glycine, proline, alanine, and leucine. The minimal necrotizing dose of the toxin was about 1 ng of protein, and the 50% lethal dose per mouse was 0.2 micrograms. The purified DNT was heat labile and sensitive to inactivation by trypsin, Formalin, and glutaraldehyde.