The mitogenic toxin fromPasteurella multocida(PMT) is a member of the dermonecrotic toxin family, which includes toxins fromBordetella, Escheri-chia coliandYersinia. Members of the dermonecrotic toxin family modu-late G-protein targets in host cells through selective deamidation and⁄or transglutamination of a critical active site Gln residue in the G-protein tar-get, which results in the activation of intrinsic GTPase activity.