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Accueil > Départements > Biochimie, Biophysique et Biologie Structurale > Herman VAN TILBEURGH : Fonction et Architecture des Assemblages Macromoléculaires

Protéines non structurées et leur transition vers un état structuré

Principal Investigator : Dominique Durand

Version française en cours

How can we study an unstructured protein that gets structure upon ligand binding ? Small-Angle X-ray Scattering (SAXS) is a technique of choice to obtain rapidly the global parameters characterizing an unstructured protein and reveal its conformational changes (for a review, see for instance "How random are intrinsically disordered proteins ? A Small angle scattering perspective", V. Receveur-Bréchot and D. Durand, Curr Protein Pept Sci. 13(2012) 55-75).

The SAXS pattern provides a description of the protein in terms of a statistical polymer when it is unstructured and allows one to propose a model for the conformations of the structured regions when it acquires structure.
Two lines of research are explored by the group in this field :

Basic salivary proteins :
Collaboration : M. Skepö, C. Cragnell (Lund University), B. Cabane, ESPCI

IB5 and the tannin EgCG
Aggregation of the salivary proline-rich protein IB5 in presence of the tannin EgCG : F. Canon, F. Paté, V. Cheynier, P. Sarni-Manchado, A. Giuliani, J. Pérez, D. Durand, J. Li, B. Cabane, Langmuir 29 (2013)1926-1937

They are fully unstructured proteins whose main property is to bind tannins. These proline rich proteins behave like « wormlile chains » with a large persistence length that facilitates tannin access for binding. Some form aggregates when binding tannins (see the Figure to the right) while others form spherical micelles with a well-defined diameter. Our work is currently focused on a small salivary protein, histatin, that exhibits antibacterial and antifungal properties. We try to determine whether these properties are associated with the unstructured state of the protein.

Structural transition upon calcium binding of the receptor binding domain of the CyaA toxin from Bordetella Pertussis

Collaboration : group of A. Chenal (Institut Pasteur). This domain comprising a large number of so-called RTX motifs is fully unstructured in the absence of calcium. Upon calcium addition, the RTX motifs form β-strands as revealed by far UV circular dichroÏsm and FTIR.
The analysis of the scattering pattern shows that the protein behaves as a polymeric chain of blobs in the absence of calcium and as a well structured object in
the presence of calcium as indicated by the Porod law in 1/q4 at large angles (red curve and black line in the figure).
The SAXS analysis is coupled to HD exchange-mass spectrometry experiments.


DURAND Dominique [Directeur de Recherche - CNRS]
Fonction et Architecture des Assemblages Macromoléculaires
01 69 82 62 16 Orsay - Bât 430

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