The pH becomes more acidic withing the endosome triggering the partial unfolding of the protein. After the fragment A is delivered to the cytoplasm, it refolds and becomes active. Once all the host's EF-2 molecules are complexed, cell death will occur. Uptake and activity of diphtheria toxin in Eukaryotic cells. Figure taken from Dr. Kenneth Todar's lecture topic s for bacteriology at the University of Wisconsin.
T is the hydrophobic or transmembrane domain that inserts into the cell membrane.
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