"Vibrio parahaemolyticus" is a Gram-negative bacterium that causes food poisoning as a result of raw or undercooked seafood consumption in humans. VopS, a type III effector found in "Vibrio parahaemolyticus", contains a Fic domain that has a conserved HPFx(D/E)GN(G/K)R motif that contains a histidine residue essential for AMPylation. VopS blocks actin assembly by modifying threonine residue in the switch 1 region of Rho GTPases. The transfer of an AMP moiety using ATP to the threonine residue results in steric hindrance, and thus prevents Rho GTPases from interacting with downstream effectors. As a result, the host cell’s actin cytoskeleton control is disabled, leading to cell rounding.