Conformational Ensembles from Experimental Data and Computer Simulations

Conformational Ensembles from Experimental Data and Computer Simulations

Poster Abstracts

37-POS Board 37 Functional Role of the TCTP Intrinsically Disordered Region Investigated by MD Simulations and NMR Experiments Florian Malard 1 , Nadine Assrir 1 , Ewen Lescop 1 , Mouad Alami 2 , Samir Messaoudi 2 , Tâp Ha- Duong 2 . 1 CNRS, Gif-sur-Yvette, France, 2 Université Paris-Sud, Châtenay-Malabry, France. The translationally controlled tumor protein (TCTP) is involved in several biological processes. To exert its various functions, TCTP is brought to interact with many other biomolecules. Notably, TCTP residues S46 and S64 can be phosphorylated, impacting its binding with other proteins. Moreover, TCTP can sequestrate calcium to block the calcium-dependent apoptosis process. However, little information on the quaternary structures of TCTP complexes are available, impeding the full understanding of the mechanisms by which TCTP performs its functions. The protein three-dimensional structure is composed of a core domain and an intrinsically disordered loop which contains a highly conserved TCTP signature. The objective of this study is to explore this disordered loop conformational ensemble, using molecular dynamics simulations in combination with NMR experiments, to gain a better insight into its functional role. The TCTP conformational ensemble was studied under four conditions: without or with calcium, with residue S46 phosphorylated, and with both S46 and S64 phosphorylated. Simulations show that, in the absence of calcium, the non-phosphorylated and pS46 protein have overall similar conformational ensemble. The double phosphorylated pS46-pS64 protein is more extended, whereas calcium induce a more compact structure. However, in all conditions, the disordered loop has a similar extent, but is more or less bound to the core domain, hiding accessible surface area from TCTP partners. Simulations also permit to identify calcium binding sites on TCTP which were partially confirmed by NMR experiments. In conclusion, the TCTP intrinsically disordered loop might play the role of a switch which could interfere with the binding of its multiple partners. Its conformational states depend on the presence of calcium and on the phosphorylation of residues S46 and S64.

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