Critical Residues of Clostridium perfringens Delta-Toxin for Oligomerization and Receptor Binding

Delta-toxin produced by Clostridium perfringens types B and C is a β-pore-forming cytotoxin. Here, using site-directed mutagenesis, we identified the amino acid residues that contribute to delta-toxin oligomerization and binding. We replaced Lys-43 and Ser-109 located in the β-sandwich domain and Arg-200 located in the rim domain. Substitution of alanine for Ser-109 caused reductions in both cytotoxicity and oligomerization. However, exchange of Lys-43 for alanine resulted in a reduction in the cytotoxicity. Replacement of Arg-200 with alanine led to drastic reductions cytotoxicity and cell binding. Our results demonstrate that Ser-109 plays a role in oligomerization, and that Arg-200 is critical for binding of the toxin.