Clostridium difficile toxin B (TcdB)

Toxin B (TcdB) is a cytotoxin that has a molecular weight of 270 kDa and an isoelectric point, pl, of 4.1. Toxin B has four different structural domains: catalytic, cysteine protease, translocation, and receptor binding. The N-terminal glucosyltransferase catalytic domain includes amino acid residues 1-544 while the cysteine protease domain includes residues 545-801. Additionally, the translocation region incorporates amino acid residues from 802-1664 while the receptor binding region is part of the C-terminal region and includes amino acid residues from 1665 to 2366. Schematic image of the TcdB protein sequence. Catalytic region shown in blue contains residues 1-543, the cysteine protease region shown in black contains residues 544-801, the translocation region shown in red contains residues 802-1664, and the receptor binding region shown in green contain residues 1665-2366.