Kinetic characterization of VopT, a mono-ADP-ribosyltransferase toxin from Vibrio parahaemolyticus

Pathogenic bacteria cause many human infections, and most employ virulence factors that cause cell or tissue damage in the host. One important virulence factor group is the mono-ADP-ribosyltransferase (mART) family. Vibrio parahaemolyticus is a pathogenic bacterium that encodes a virulence factor, VopT, a mART toxin. VopT modifies Ras, a small GTPase involved in cell signaling, leading to intestinal epithelial tissue damage. VopT is classified as an ExoS-like toxin as it requires the binding of a 14-3-3 protein for activation and shares high sequence identity to other ExoS-like members. Glycohydrolase activities were assessed for wild-type and catalytic variants, the first inhibitors of VopT were identified with IC50 values between 4 and 45 µM, and an ExoT homology model was produced that provides insight into the FAS-dependent activity of VopT. Characterization of VopT has increased our understanding of mART enzymes and may lead to the development of effective therapeutic compounds.