Translocation of the catalytic domain of diphtheria toxin across planar phospholipid bilayers by its own T domain

The T domain of diphtheria toxin is known to participate in the pH-dependent translocation of the catalytic C domain of the toxin across the endosomal membrane, but how it does so, and whether cellular proteins are also required for this process, remain unknown. Here, we report results showing that the T domain alone is capable of translocating the entire C domain across model, planar phospholipid bilayers in the absence of other proteins. The T domain therefore contains the entire molecular machinery for mediating transfer of the catalytic domain of diphtheria toxin across membranes.