Difference in resistance of subunits A and B ofVibrio cholerae toxin (choleragen) to treatment with pronase

Disc electrophoresis in sodium dodecyl sulphate, performed on choleragen after incubation with pronase, only showed the band corresponding to the B subunit, while the A subunit was lost. When examined in immunodiffusion, the digested choleragen was still able to precipitate with specific antibodies. On the other hand, toxicity was considerably reduced.