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Propriétés électrostatiques et structurales des protéines diffractant à haute résolution

Abstract : This study is about the electrostatic and structural properties of proteins diffracting at high X-ray resolution. Two different aspects are tackled which are 1) the analysis of properties derived from their charge distribution, parting from a fundamental point of view and 2) the application of methods used in high resolution macromolecular crystallography to two enzymes of major interest. After the analysis of the structure and electrostatic properties of PfluDING protein, the binding mode of a phosphate ion, located in the active site, was elucidated at two different pH values. Particularly, this study demonstrates that a diffuse hydrogen bond assures the protonation state of the phosphate ion, which is thus identical at each pH value. The second enzyme studied is the proteine DFPase which is capable of hydrolysing nerve agents. A high resolution X-ray structure and a medium resolution neutron structure where compared. The analysis points out the differences between the two models and a new catalytic mechanism could be proposed. The more fundamental aspects of this study are about the secondary structural elements of proteins: their electrostatic properties in terms of electrostatic moments (dipole and quadrupole moments of helices and sheets) as well as the hydrogen bond network assuring the cohesion of helices have been analyzed. It has been shown that certain interactions between peptide units within helices, represented usually as hydrogen bonds, should actually be considered as pure electrostatic contacts
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https://hal.univ-lorraine.fr/tel-01746343
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Dorothée Liebschner. Propriétés électrostatiques et structurales des protéines diffractant à haute résolution. Autre. Université Henri Poincaré - Nancy 1, 2010. Français. ⟨NNT : 2010NAN10085⟩. ⟨tel-01746343⟩

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