Heterogeneity among heat-labile enterotoxins produced by porcine enterotoxigenic Escherichia coli.

The heat-labile enterotoxins (LT) produced by various porcine strains (LTp) of enterotoxigenic Escherichia coli were purified to homogeneity and their molecular properties were compared with each other. By double gel diffusion and rabbit skin permeability test, LTps from WT-1 (LTp-WT-1) and BO-149 (LTp-BO-149) strains were antigenically and biologically identical. By polyacrylamide gel electrophoresis with sodium dodecyl sulfate (SDS), the mobilities of A and B subunits of LTp (BO-149) were identical to those of LTp (WT-1). However, on polyacrylamide gel electrophoresis without SDS, LTp (BO-149) and LTp (WT-1) differed in mobility, suggesting their molecular differences. Though the pI value of the B subunit of LTp (BO-149) was identical to that of LTp (WT-1), the pI value of the A subunit of LTp (BO-149) was higher than that of LTp (WT-1). These data suggest that there is molecular heterogeneity among LTps produced by the two porcine enterotoxigenic Escherichia coli strains.