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Interactions faibles protéine – protéine en solution : La malate déshydrogénase halophile

Abstract : The cell is a crowded environment in which interactions between macromolecules, even weak interactions, determine their solubility and the assembly of the labile complexes that operate biological functions. The weak interactions between proteins in solution that define their non-ideal behaviour also control their crystallisation.
To which extent do protein – solvent interactions influence protein – protein interactions ? In the present thesis, these two kinds of interaction have been put in relation for the malate dehydrogenase (Hm MalDH) from Haloarcula marismortui. This halophilic protein is very acidic and is solvated by large amounts of water and salt.
We have developed a new method for the determination of the second virial coefficient A2 by modelling the sedimentation velocity profiles in analytical ultracentrifugation. It allows to study complex solvent compositions with small amounts of protein.
The protein – protein interactions of Hm MalDH in various salt solvents were characterised by smallangle scattering of neutrons or X-rays. The A2 and the solution structure factors were analysed with DLVO-like interaction potentials. The repulsive interactions arise mainly from the excluded-volume term and to a lesser extent from the electrostatic term. The attractive interactions appear to be qualitatively correlated to positive or negative values of the preferential salt biding parameters. These results also allow to explain the molecular adaptation of halophilic proteins that require a solvation rich in salt in order to remain soluble.
The crystallisation by dilution of Hm MalDH in various mixture of salt – MPD (2-methy-2,4-pentanediol) is correlated with a slow evolution from repulsive to moderately attractive protein – protein interactions. MPD modifies the protein – protein interactions by adding an attractive term that arises from the repulsion of MPD by the charges on the protein.
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Contributor : Lionel Costenaro <>
Submitted on : Thursday, December 9, 2004 - 4:28:20 PM
Last modification on : Wednesday, October 14, 2020 - 4:18:51 AM
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Lionel Costenaro. Interactions faibles protéine – protéine en solution : La malate déshydrogénase halophile. Biochimie [q-bio.BM]. Université Joseph-Fourier - Grenoble I, 2001. Français. ⟨tel-00007698⟩

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