Mutational analysis of the enzymatic domain of Clostridium difficile toxin B reveals novel inhibitors of the wild-type toxin.

Toxin B (TcdB), a major Clostridium difficile virulence factor, glucosylates and inactivates the small GTP-binding proteins Rho, Rac, and Cdc42. In the present study we provide evidence that enzymatically inactive fragments of the TcdB enzymatic domain are effective intracellular inhibitors of native TcdB. Site-directed and deletion mutants of the TcdB enzymatic region (residues 1 to 556), lacking receptor binding and cell entry domains, were analyzed for attenuation of glucosyltransferase and glucosylhydrolase activity.

Clostridium difficile toxin B activates dual caspase-dependent and caspase-independent apoptosis in intoxicated cells.

Clostridium difficile toxin B (TcdB) inactivates the small GTPases Rho, Rac and Cdc42 during intoxication of mammalian cells. In the current work, we show that TcdB has the potential to stimulate caspase-dependent and caspase-independent apoptosis. The apoptotic pathways became evident when caspase-3-processed-vimentin was detected in TcdB-treated HeLa cells.