@article {2018|2087, title = {The major β-catenin/E-cadherin junctional binding site is a primary molecular mechano-transductor of differentiation .}, journal = {Elife}, volume = {7}, year = {2018}, month = {2018 07 19}, abstract = {

, the primary molecular mechanotransductive events mechanically initiating cell differentiation remain unknown. Here we find the molecular stretching of the highly conserved Y654-β-catenin-D665-E-cadherin binding site as mechanically induced by tissue strain. It triggers the increase of accessibility of the Y654 site, target of the Src42A kinase phosphorylation leading to irreversible unbinding. Molecular dynamics simulations of the β-catenin/E-cadherin complex under a force mimicking a 6 pN physiological mechanical strain predict a local 45\% stretching between the two α-helices linked by the site and a 15\% increase in accessibility of the phosphorylation site. Both are quantitatively observed using FRET lifetime imaging and non-phospho Y654 specific antibody labelling, in response to the mechanical strains developed by endogenous and magnetically mimicked early mesoderm invagination of gastrulating embryos. This is followed by the predicted release of 16\% of β-catenin from junctions, observed in FRAP, which initiates the mechanical activation of the β-catenin pathway process.

}, keywords = {Amino Acid Sequence, Animals, Armadillo Domain Proteins, Binding Sites, Cadherins, Cell Differentiation, Drosophila melanogaster, Drosophila Proteins, Fluorescence Resonance Energy Transfer, Mechanotransduction, Cellular, Molecular Dynamics Simulation, Phosphorylation, Protein Binding, Protein Conformation, Proto-Oncogene Proteins pp60(c-src), Sequence Homology, Transcription Factors}, issn = {2050-084X}, doi = {10.7554/eLife.33381}, author = {R{\"o}per, Jens-Christian and Mitrossilis, D{\'e}mosth{\`e}ne and Guillaume Stirnemann and Waharte, Fran{\c c}ois and Brito, Isabel and Fernandez-Sanchez, Maria-Elena and Marc Baaden and Salamero, Jean and Farge, Emmanuel} } @article {2017|2023, title = {Mechanics of Protein Adaptation to High Temperatures}, journal = {J Phys Chem Lett}, volume = {8}, year = {2017}, month = {Dec}, pages = {5884-5890}, abstract = {

Inspired by Somero\&$\#$39;s corresponding state principle that relates protein enhanced thermal stability with mechanical rigidity, we deployed state of the art computational techniques (based on atomistic steered molecular dynamics and Hamiltonian-replica exchange simulations) to study the in silico realization of mechanical and thermal unfolding of two homologous Csp proteins that have evolved to thrive in different thermal environments. By complementing recent single-molecule experiments, we unambiguously show that, for these homologues whose structures are very similar, the increased thermal resistance of the thermophilic variant is not associated with an increased mechanical stability. Our approach provides microscopic insights that are otherwise inaccessible to experimental techniques, and explains why the protein weak spots for thermal and mechanical denaturation are distinct.

}, doi = {10.1021/acs.jpclett.7b02611}, author = {Guillaume Stirnemann and Sterpone, Fabio} } @article {2015|1729, title = {The mechanochemistry of copper reports on the directionality of unfolding in model cupredoxin proteins.}, journal = {Nature Comm.}, volume = {6}, year = {2015}, pages = {7894}, abstract = {

Understanding the directionality and sequence of protein unfolding is crucial to elucidate the underlying folding free energy landscape. An extra layer of complexity is added in metalloproteins, where a metal cofactor participates in the correct, functional fold of the protein. However, the precise mechanisms by which organometallic interactions are dynamically broken and reformed on (un)folding are largely unknown. Here we use single molecule force spectroscopy AFM combined with protein engineering and MD simulations to study the individual unfolding pathways of the blue-copper proteins azurin and plastocyanin. Using the nanomechanical properties of the native copper centre as a structurally embedded molecular reporter, we demonstrate that both proteins unfold via two independent, competing pathways. Our results provide experimental evidence of a novel kinetic partitioning scenario whereby the protein can stochastically unfold through two distinct main transition states placed at the N and C termini that dictate the direction in which unfolding occurs.

}, isbn = {doi:10.1038/ncomms8894}, issn = {2041-1723}, doi = {10.1038/ncomms8894}, url = {http://www.nature.com/ncomms/2015/150803/ncomms8894/abs/ncomms8894.html}, author = {Beedle, Amy E M and Lezamiz, Ainhoa and Guillaume Stirnemann and Garcia-Manyes, Sergi} } @article {2013|1670, title = {Mechanisms of acceleration and retardation of water dynamics by ions}, journal = {J. Am. Chem. Soc.}, volume = {135}, year = {2013}, pages = {11824{\textendash}11831}, abstract = {

There are fundamental and not yet fully resolved questions concerning the impact of solutes, ions in particular, on the structure and dynamics of water, which can be formulated as follows: Are the effects of ions local or long-ranged? Is the action of cations and anions on water cooperative or not? Here, we investigate how the reorientation and hydrogen-bond dynamics of water are affected by ions in dilute and concentrated aqueous salt solutions. By combining simulations and analytic modeling, we first show that ions have a short-ranged influence on the reorientation of individual water molecules and that depending on their interaction strength with water, they may accelerate or slow down water dynamics. A simple additive picture combining the effects of the cations and anions is found to provide a good description in dilute solutions. In concentrated solutions, we show that the average water reorientation time ceases to scale linearly with salt concentration due to overlapping hydration shells and structural rearrangements which reduce the translational displacements induced by hydrogen-bond switches and increase the solution viscosity. This effect is not ion-specific and explains why all concentrated salt solutions slow down water dynamics. Our picture, which is demonstrated to be robust vis-a-vis a change in the force-field, reconciles the seemingly contradictory experimental results obtained by ultrafast infrared and NMR spectroscopies, and suggests that there are no long-ranged cooperative ion effects on the dynamics of individual water molecules in dilute solutions.

}, issn = {00027863}, author = {Guillaume Stirnemann and Wernersson, Erik and Jungwirth, Pavel and Laage, Damien} } @article {2012|1488, title = {Magnitude and molecular origin of water slowdown next to a protein}, journal = {J. Am. Chem. Soc.}, volume = {134}, year = {2012}, pages = {4116{\textendash}4119}, abstract = {

Hydration shell dynamics plays a critical role in protein folding and biochemical activity and has thus been actively studied through a broad range of techniques. While all observations concur with a slowdown of water dynamics relative to the bulk, the magnitude and molecular origin of this retardation remain unclear. Via numerical simulations and theoretical modeling, we establish a molecular description of protein hydration dynamics and identify the key protein features that govern it. Through detailed microscopic mapping of the water reorientation and hydrogen-bond (HB) dynamics around lysozyme, we first determine that 80\% of the hydration layer waters experience a moderate slowdown factor of \~{}2-3, while the slower residual population is distributed along a power-law tail, in quantitative agreement with recent NMR results. We then establish that the water reorientation mechanism at the protein interface is dominated by large angular jumps similar to the bulk situation. A theoretical extended jump model is shown to provide the first rigorous determination of the two key contributions to the observed slowdown: a topological excluded-volume factor resulting from the local protein geometry, which governs the dynamics of the fastest 80\% of the waters, and a free energetic factor arising from the water-protein HB strength, which is especially important for the remaining waters in confined sites at the protein interface. These simple local factors are shown to provide a nearly quantitative description of the hydration shell dynamics.

}, issn = {00027863}, author = {Fabio Sterpone and Guillaume Stirnemann and Laage, Damien} }