The Escherichia coli Cytotoxic Necrotizing Factors, CNF1, CNF2, CNF3 and CNFY from Yersinia pseudotuberculosis belong to a family of deamidating toxins. CNFs deamidate glutamine 63/61 in the switch II region of Rho GTPases that is essential for GTP hydrolysing activity. Deamidation leads to constitutive activation of Rho GTPases. However, cellular mechanisms like proteasomal degradation of the activated Rho proteins restrict the action of the GTPases. This review describes the differences between the toxin family members concerning expression, cellular entry and substrate specificity.
Keywords: CNF; Rho GTPase activation; bacterial toxin; deamidation.