Clostridium difficile toxin B
A 270 kD cytotoxin produced by Clostridium difficile that is 1000-fold more cytotoxic than C difficile toxin A. It has four–catalytic, cysteine protease, translocation, and receptor binding–domains, of which the catalytic domain is the most damaging.
Mechanism Catalytic activation of glucosyltransferase deactivates small GTPases–e.g. Rho, Rac and Cdc42–leading to defective signal transduction, and dysfunction of actin cytoskeleton, cell-cell junction, and apoptosis.