CNF1 and CNF2 belong to a family of bacterial toxins that target the small GTP-binding Rho proteins that regulate the actin cytoskeleton. Members of this toxin family typically inactivate Rho; however, CNF1 and the highly related CNF2, activate Rho by deamidation. CNF1 is more frequently associated with E.coli strains that cause extraintestinal infections in humans, particularly those of the urinary tract. In CNF1-producing uropathogenic E.coli strains, CNF1 is chromosomally encoded and typically resides on a pathogenic island that also contains hemolysin and P fimbria-related genes. Both CNF1 and the highly related CNF2 are monomeric, cytoplasmic toxins of approximately 115 kDa. CNF1 can be structurally organised into 3 functional domains : the N-terminal, central and C-terminal domains. The latter exhibits the catalytic activity of the toxin.