Cytosolic Delivery and Characterization of the TcdB Glucosylating Domain by Using a Heterologous Protein Fusion

Abstract
TcdB from Clostridium difficile glucosylates small GTPases (Rho, Rac, and Cdc42) and is an important virulence factor in the human disease pseudomembranous colitis. In these experiments, in-frame genetic fusions between the genes for the 255 amino-terminal residues of anthrax toxin lethal factor (LFn) and the TcdB1-556 coding region were constructed, expressed, and purified from Escherichia coli. LFnTcdB1-556was enzymatically active and glucosylated recombinant RhoA, Rac, Cdc42, and substrates from cell extracts. LFnTcdB1-556 plus anthrax toxin protective antigen intoxicated cultured mammalian cells and caused actin reorganization and mouse lethality, all similar to those caused by wild-type TcdB.