Histidine residues in Clostridium perfringens epsilon toxin

Clostridium perfringens epsilon toxin was inactivated by ethoxyformic anhydride.A histidyl residue in the toxin was carbethoxylated under the conditions in\ which the toxin was completely inactivated, whereas tyrosyl residues were not affected.The toxin inactivated by ethoxyformic anhydride (EFA) was reactivated by treatment with hydroxylamine.These results indicated that a histidyl residue in the toxin is essential for its lethal activity.