A CIRCULAR-DICHROISM STUDY OF THE ENTEROTOXIN FROM CLOSTRIDIUM PERFRINGENS TYPE A

Far-UV circular-dichroism spectra of the enterotoxin from Clostridium perfringens type A were recorded under different conditions, and conformational analysis was performed. The native enterotoxin (pH 6.8) was shown to contain about 80% pleated sheet, 20% random coil and no helix structure. By adding small amounts of the detergent sodium dodecyl sulfate (0–261 mol SDS/mol enterotoxin), the β-sheet structure could gradually be changed to a more α-helical structure. Treatment with 8 M urea resulted in limited alterations of the secondary structure of the enterotoxin, while heat treatment (60°C, 30 min), treatment with 6.5 M guanidine hydrochloride or 0.01 M NaOH led to a dramatic increase in the amount of random coil.