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Theses

Mecanisme de translocation de la toxine diphtérique

Abstract : Diphtheria toxin (DT) is a bacterial toxin with intracellular target, secreted by Corynebacterium diphtheriae. During cell intoxication, the translocation domain of DT (T) inserts into the endosomal membrane under acidic conditions and assists the translocation of the catalytic (C) domain in the cytosol. T undergoes conformational changes and adopts a molten globule (MG) state, competent for the interaction with the membrane.
We first identified by mutagenesis the residues in the T domain whose protonation triggers the formation of the MG state in solution and the interaction with the membrane. The results showed that the concerted protonation of the six histidines in the T domain is implicated. We found that the pair His223-257 et His251 are more implicated in the formation of the MG state in solution and that the pair His322-323 (and His251) is more implicated in the interaction with the membrane.
We then studied the conformational changes of both C and T domains within a CT protein corresponding to the whole toxin truncated at the R domain to understand the effects of the covalent link between the two domains on the conformations of C and T as a function of pH. We produced two Trp mutants, CTW50/153F and CTW206/281F, that allow to follow up the Trp fluorescence of each domain in the CT protein. The results showed that the T domain leads the way in the first steps of translocation (MG formation, binding and membrane insertion), and that it may play the role of a membrane chaperone by stabilizing the MG state of C.
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https://tel.archives-ouvertes.fr/tel-00364213
Contributor : Celine Lentz <>
Submitted on : Wednesday, February 25, 2009 - 2:24:07 PM
Last modification on : Monday, February 10, 2020 - 6:12:52 PM
Long-term archiving on: : Tuesday, June 8, 2010 - 8:18:59 PM

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  • HAL Id : tel-00364213, version 1

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Citation

Anne Chassaing. Mecanisme de translocation de la toxine diphtérique. Sciences du Vivant [q-bio]. Museum national d'histoire naturelle - MNHN PARIS, 2008. Français. ⟨tel-00364213⟩

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