Figure 1.

Domains of TcdA and TcdB and construction of mTcd138. (A) Both toxins share similar domains, including the glucosyltransferase domain (GT), the autocatalytic cysteine proteinase domain (CPD), the translocation domain (TMD) and the receptor binding domain (RBD). The DXD motif and a conserved tryptophan in the GT are involved in the enzymatic activity. (B) mTcd138 was constructed by fusing the GT and CPD of TcdB with the RBD of TcdA. Two point mutations were made in the GT of TcdB to eliminate the toxicity of mTcd138.