@article {2018|2134, title = {DNA Binding Induces a Nanomechanical Switch in the RRM1 Domain of TDP-43}, journal = {J Phys Chem Lett}, volume = {9}, year = {2018}, month = {Jul}, pages = {3800-3807}, abstract = {

Understanding the molecular mechanisms governing protein-nucleic acid interactions is fundamental to many nuclear processes. However, how nucleic acid binding affects the conformation and dynamics of the substrate protein remains poorly understood. Here we use a combination of single molecule force spectroscopy AFM and biochemical assays to show that the binding of TG-rich ssDNA triggers a mechanical switch in the RRM1 domain of TDP-43, toggling between an entropic spring devoid of mechanical stability and a shock absorber bound-form that resists unfolding forces of \∼40 pN. The fraction of mechanically resistant proteins correlates with an increasing length of the TG n oligonucleotide, demonstrating that protein mechanical stability is a direct reporter of nucleic acid binding. Steered molecular dynamics simulations on related RNA oligonucleotides reveal that the increased mechanical stability fingerprinting the holo-form is likely to stem from a unique scenario whereby the nucleic acid acts as a \"mechanical staple\" that protects RRM1 from mechanical unfolding. Our approach highlights nucleic acid binding as an effective strategy to control protein nanomechanics.

}, doi = {10.1021/acs.jpclett.8b01494}, author = {Wang, Yong Jian and Rico-Lastres, Palma and Lezamiz, Ainhoa and Mora, Marc and Solsona, Carles and Guillaume Stirnemann and Garcia-Manyes, Sergi} } @article {2018|2132, title = {The force-dependent mechanism of DnaK-mediated mechanical folding}, journal = {Sci Adv}, volume = {4}, year = {2018}, month = {Feb}, pages = {eaaq0243}, abstract = {

It is well established that chaperones modulate the protein folding free-energy landscape. However, the molecular determinants underlying chaperone-mediated mechanical folding remain largely elusive, primarily because the force-extended unfolded conformation fundamentally differs from that characterized in biochemistry experiments. We use single-molecule force-clamp spectroscopy, combined with molecular dynamics simulations, to study the effect that the Hsp70 system has on the mechanical folding of three mechanically stiff model proteins. Our results demonstrate that, when working independently, DnaJ (Hsp40) and DnaK (Hsp70) work as holdases, blocking refolding by binding to distinct substrate conformations. Whereas DnaK binds to molten globule-like forms, DnaJ recognizes a cryptic sequence in the extended state in an unanticipated force-dependent manner. By contrast, the synergetic coupling of the Hsp70 system exhibits a marked foldase behavior. Our results offer unprecedented molecular and kinetic insights into the mechanisms by which mechanical force finely regulates chaperone binding, directly affecting protein elasticity.

}, doi = {10.1126/sciadv.aaq0243}, author = {Perales-Calvo, Judit and Giganti, David and Guillaume Stirnemann and Garcia-Manyes, Sergi} } @article {2018|2136, title = {Forcing the reversibility of a mechanochemical reaction}, journal = {Nat Commun}, volume = {9}, year = {2018}, month = {08}, pages = {3155}, abstract = {

Mechanical force modifies the free-energy surface of chemical reactions, often enabling thermodynamically unfavoured reaction pathways. Most of our molecular understanding of force-induced reactivity is restricted to the irreversible homolytic scission of covalent bonds and ring-opening in polymer mechanophores. Whether mechanical force can by-pass thermodynamically locked reactivity in heterolytic bimolecular reactions and how this impacts the reaction reversibility remains poorly understood. Using single-molecule force-clamp spectroscopy, here we show that mechanical force promotes the thermodynamically disfavored SN2 cleavage of an individual protein disulfide bond by poor nucleophilic organic thiols. Upon force removal, the transition from the resulting high-energy unstable mixed disulfide product back to the initial, low-energy disulfide bond reactant becomes suddenly spontaneous, rendering the reaction fully reversible. By rationally varying the nucleophilicity of a series of small thiols, we demonstrate how force-regulated chemical kinetics can be finely coupled with thermodynamics to predict and modulate the reversibility of bimolecular mechanochemical reactions.

}, doi = {10.1038/s41467-018-05115-6}, author = {Beedle, Amy E M and Mora, Marc and Davis, Colin T and Snijders, Ambrosius P and Guillaume Stirnemann and Garcia-Manyes, Sergi} } @article {2017|2026, title = {Tailoring protein nanomechanics with chemical reactivity}, journal = {Nat Commun}, volume = {8}, year = {2017}, month = {Jun}, pages = {15658}, abstract = {

The nanomechanical properties of elastomeric proteins determine the elasticity of a variety of tissues. A widespread natural tactic to regulate protein extensibility lies in the presence of covalent disulfide bonds, which significantly enhance protein stiffness. The prevalent in vivo strategy to form disulfide bonds requires the presence of dedicated enzymes. Here we propose an alternative chemical route to promote non-enzymatic oxidative protein folding via disulfide isomerization based on naturally occurring small molecules. Using single-molecule force-clamp spectroscopy, supported by DFT calculations and mass spectrometry measurements, we demonstrate that subtle changes in the chemical structure of a transient mixed-disulfide intermediate adduct between a protein cysteine and an attacking low molecular-weight thiol have a dramatic effect on the protein\&$\#$39;s mechanical stability. This approach provides a general tool to rationalize the dynamics of S-thiolation and its role in modulating protein nanomechanics, offering molecular insights on how chemical reactivity regulates protein elasticity.

}, doi = {10.1038/ncomms15658}, author = {Beedle, Amy E M and Mora, Marc and Lynham, Steven and Guillaume Stirnemann and Garcia-Manyes, Sergi} } @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} }