ROLES OF THE CARBOXY-TERMINAL REGION OF CLOSTRIDIUM-PERFRINGENS ALPHA-TOXIN

Treatment of Clostridium perfringens alpha toxin with aminopeptidase r esulted in no effect on various activities of the toxin. Aminopeptidas e did not hydrolyze the native toxin or the toxin treated with urea in the presence of EDTA. Treatment with carboxypeptidase for 30 min resu lted in a 75% decrease in these activities. Incubation of the native t oxin 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 (AT(1-350)) showed about 59-87% of the activity of native toxin. The mutant toxin showed partial antigenic identity with the native toxin. These data su ggest that the C-terminal domain contributes to maintaining the active form of the toxin.