Molecular properties of cholera enteroxin.

The molecular properties of Vibrio cholerae enterotoxin obtained from two different insitutions were studied. The preparations, which were purified by different methods, showed the same physicochemical properties. Ultracentrifugal analysis showed that the toxin had a molecular weight of 79,000, a sedimentation coefficient of 5.25 S and a diffusion coefficient of 6.02 D. When the toxin was subjected to polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, the A subunit with an apparent molecular weight of 31,000-32,000 was observed. Based of these findings and the molecular weight of the B subunit of 11,604 which was calculated from its primary structure, it is proposed that holotoxin is composed of one A subunit and four B subunits.