Interaction of Diphtheria Toxin T Domain with Molten Globule-Like Proteins and Its Implications for Translocation

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Science  07 May 1999:
Vol. 284, Issue 5416, pp. 955-957
DOI: 10.1126/science.284.5416.955

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The transmembrane (T) domain of diphtheria toxin has a critical role in the low pH–induced translocation of the catalytic domain (A chain) of the toxin across membranes. Here it is shown that at low pH, addition of proteins in a partly unfolded, molten globule-like conformation converted the T domain from a shallow membrane-inserted form to its transmembrane form. Fluorescence energy transfer demonstrated that molten globule-like proteins bound to the T domain. Thus, the T domain recognizes proteins that are partly unfolded and may function in translocation of the A chain as a transmembrane chaperone.

  • * These authors contributed equally to this work.

  • To whom correspondence should be addressed. E-mail: elondon{at}

  • Present address: Aaron Diamond AIDS Research Center, 455 First Avenue, New York, NY 10016, USA.

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