Penetration of protein toxins into cells

AB toxins deliver their enzymatically active A domain to the cytosol. Some AB-toxins are able to penetrate cellular membranes from endosomes where the low pH triggers their translocation. One such toxin is diphtheria toxin and important features of its translocation mechanism have been unraveled during the last year, Other toxins depend on retrograde transport through the secretory pathway to the ER before translocation, and recent findings suggest that these toxins take advantage of the ER translocation machinery normally used for transport of cellular proteins, In addition, the intracellular targets of many of these toxins have been identified recently.