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Structural studies of virulence factors from the bacterium Helicobacter pylori

Abstract : H. pylori is a bacterium that infects the stomach of half of the world population. It is involved in most gastric diseases, in particular ulcers and the stomach cancer. The bacterium produces two toxins, CagA and Tipα, that associate with gastric cancer development. CagA is injected inside the cells and interacts with several proteins from signaling pathways. Tipα is secreted by H. pylori and internalized by the gastric cells, where it induces the production of proinflammatory cytokines. In this thesis, we have first studied the interactions between a central domain of CagA and proteins from H. pylori. We have then used a novel High- Throughput methodology to determine new soluble CagA fragments. One of them, corresponding to a C-terminal domain of 33kDa (CagAC33), has been characterized by using biochemical and biophysical techniques. CagAC33 forms a dimer of dimers in solution and particles in electron microscopy. Moreover, CagAC33 can be phosphorylated in vitro by the c-Src and c-Abl kinases, but the phosphorylation efficiency depends on the kinase. The study of the interaction between P-CagA and the SHP-2 phosphatase shows that CagA is dephosphorylated in vitro. We have also solved the structures of two crystal forms of Tipα by X-ray crystallography. The structure of Tipα monomer adopts a novel fold and the protein forms different dimers in the two crystal forms. The study of Tipα in solution indicates that one of the crystallographic dimers is likely favored and suggests that the disulfide bridges identified in the N- terminal portion of the protein have a role during the secretion.
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Contributor : Tommaso Tosi <>
Submitted on : Sunday, September 26, 2010 - 6:09:50 PM
Last modification on : Thursday, November 19, 2020 - 2:44:17 PM
Long-term archiving on: : Monday, December 27, 2010 - 2:38:10 AM


  • HAL Id : tel-00521213, version 1



Tommaso Tosi. Structural studies of virulence factors from the bacterium Helicobacter pylori. Biomolecules [q-bio.BM]. European Synchrotron Radiation Facility, 2010. English. ⟨tel-00521213⟩



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