Roles of the carboxy-terminal region of Clostridium perfringens alpha toxin.

Treatment of Clostridium perfringens alpha toxin with aminopeptidase resulted in no effect on various activities of the toxin. Aminopeptidase did not hydrolyze the native toxin or the toxin treated with urea in the presence of EDTA. Treatment with carboxypeptidase for 30 min resulted in a 75% decrease in these activities. Incubation of the native toxin with carboxypeptidase for 30 min released approximately 15 amino acids from the C-terminus of the toxin. The biological activities of a mutant toxin lacking 20 C-terminal residues of the toxin (AT1-350) showed about 59-87% of the activity of native toxin. The mutant toxin showed partial antigenic identity with the native toxin. These data suggest that the C-terminal domain contributes to maintaining the active form of the toxin.