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 an
d important features of its translocation mechanism have been unraveled dur
ing the last year, Other toxins depend on retrograde transport through the
secretory pathway to the ER before translocation, and recent findings sugge
st that these toxins take advantage of the ER translocation machinery norma
lly used for transport of cellular proteins, In addition, the intracellular
targets of many of these toxins have been identified recently.