@article {2018|2086, title = {Analyzing protein topology based on Laguerre tessellation of a pore-traversing water network.}, journal = {Sci Rep}, volume = {8}, year = {2018}, month = {2018 09 10}, pages = {13540}, abstract = {

Given the tight relation between protein structure and function, we present a set of methods to analyze protein topology, implemented in the VLDP program, relying on Laguerre space partitions built from series of molecular dynamics snapshots. The Laguerre partition specifies inter-atomic contacts, formalized in graphs. The deduced properties are the existence and count of water aggregates, possible passage ways and constrictions, the structure, connectivity, stability and depth of the water network. As a test-case, the membrane protein FepA is investigated in its full environment, yielding a more precise description of the protein surface. Inside FepA, the solvent splits into isolated clusters and an intricate network connecting both sides of the lipid bilayer. The network is dynamic, connections set on and off, occasionally substantially relocating traversing paths. Subtle differences are detected between two forms of FepA, ligand-free and complexed with its natural iron carrier, the enterobactin. The complexed form has more constricted and more centered openings in the upper part whereas, in the lower part, constriction is released: two main channels between the plug and barrel lead directly to the periplasm. Reliability, precision and the variety of topological features are the main interest of the method.

}, keywords = {Bacterial Outer Membrane Proteins, Carrier Proteins, Enterobactin, Molecular Dynamics Simulation, Protein Stability, Protein Structure, Secondary, Receptors, Cell Surface, Structure-Activity Relationship, Water}, issn = {2045-2322}, doi = {10.1038/s41598-018-31422-5}, author = {Esque, J{\'e}r{\'e}my and Sansom, Mark S P and Marc Baaden and Oguey, Christophe} } @article {2018|2094, title = {Holding the Nucleosome Together: A Quantitative Description of the DNA-Histone Interface in Solution.}, journal = {J Chem Theory Comput}, volume = {14}, year = {2018}, month = {2018 Feb 13}, pages = {1045-1058}, abstract = {

The nucleosome is the fundamental unit of eukaryotic genome packaging in the chromatin. In this complex, the DNA wraps around eight histone proteins to form a superhelical double helix. The resulting bending, stronger than anything observed in free DNA, raises the question of how such a distortion is stabilized by the proteic and solvent environments. In this work, the DNA-histone interface in solution was exhaustively analyzed from nucleosome structures generated by molecular dynamics. An original Voronoi tessellation technique, measuring the topology of interacting elements without any empirical or subjective adjustment, was used to characterize the interface in terms of contact area and occurrence. Our results revealed an interface more robust than previously known, combining extensive, long-lived nonelectrostatic and electrostatic interactions between DNA and both structured and unstructured histone regions. Cation accumulation makes the proximity of juxtaposed DNA gyres in the superhelix possible by shielding the strong electrostatic repulsion of the charged phosphate groups. Overall, this study provides new insights on the nucleosome cohesion, explaining how DNA distortions can be maintained in a nucleoprotein complex.

}, keywords = {DNA, Histones, Molecular Dynamics Simulation, Nucleosomes, Solutions, Static Electricity}, issn = {1549-9626}, doi = {10.1021/acs.jctc.7b00936}, author = {Elbahnsi, Ahmad and Retureau, Romain and Marc Baaden and Hartmann, Brigitte and Oguey, Christophe} }