Since it was first observed in late 2019, the COVID-19 pandemic has created a global emergency for national health systems due to millions of confirmed cases and hundreds of thousands of deaths. At a molecular level, the bottleneck for the infection is the binding of the receptor binding domain (RBD) of the viral spike protein to ACE2, an enzyme exposed on human cell membranes. Several experimental structures of the ACE2:RBD complex have been made available, however they offer only a static description of the arrangements of the molecules in either the free or bound states. In order to gain a dynamic description of the binding process that is key to infection, we use molecular simulations with a coarse grained model of the RBD and ACE2. We find that binding occurs in an all-or-none way, without intermediates, and that even in the bound state, the RBD exhibits a highly dynamic behaviour. From short equilibrium simulations started in the unbound state we provide snapshots that result in a tentative mechanism of binding. Our findings may be important for the development of drug discovery strategies that target the RBD. ; DDS receives financial support from the grants PGC2018-099321-B-I0 and RYC-2016- 19590 from the Spanish Ministry of Science, Research and Universities (MINECO/FEDER) and the Basque Government through grant IT588-13. The Spanish Ministry of Science, Research and Universities also supports JAG and RPJ through grants BIO2016-74875-P and BIO2016-77390-R, respectively. ; No
Cellulases catalyze the hydrolysis of cellulose. Improving their catalytic efficiency is a long-standing goal in biotechnology given the interest in lignocellulosic biomass decomposition. Although methods based on sequence alteration exist, improving cellulases is still a challenge. Here we show that Ancestral Sequence Reconstruction can "resurrect" efficient cellulases. This technique reconstructs enzymes from extinct organisms that lived in the harsh environments of ancient Earth. We obtain ancestral bacterial endoglucanases from the late Archean eon that efficiently work in a broad range of temperatures (30–90 °C), pH values (4–10). The oldest enzyme (~2800 million years) processes different lignocellulosic substrates, showing processive activity and doubling the activity of modern enzymes in some conditions. We solve its crystal structure to 1.45 Å which, together with molecular dynamics simulations, uncovers key features underlying its activity. This ancestral endoglucanase shows good synergy in combination with other lignocellulosic enzymes as well as when integrated into a bacterial cellulosome. ; We thank Prof. Ed Bayer's group for kindly providing the plasmids used in the minicellulosome constructs. Research was supported by the Basque Government grant ELKARTEK to R.P.-J, and also partly by Ministry of Economy and Competitiveness (MINECO) grant BIO2016-77390-R, BFU2015-71964 to R.P.-J., BIO2016-74875-P to J. A.G., and CTQ2015-65320-R and RYC-2016-19590 to D.D.S.; European Commission grant CIG Marie Curie Reintegration program FP7-PEOPLE-2014 to R.P.-J, and European Commission grant NMP-FP7 604530-2 (CellulosomePlus), and the ERA-IB EIB.12.022 grant (FiberFuel) funded by the MINECO (PCIN-2013-011-C02-01) to M.C.-V. We also thank Fundación Repsol and Gipuzkoako Foru Aldundia for financial support.
The sarcomere-based structure of muscles is conserved among vertebrates; however, vertebrate muscle physiology is extremely diverse. A molecular explanation for this diversity and its evolution has not been proposed. We use phylogenetic analyses and single-molecule force spectroscopy (smFS) to investigate the mechanochemical evolution of titin, a giant protein responsible for the elasticity of muscle filaments. We resurrect eight-domain fragments of titin corresponding to the common ancestors to mammals, sauropsids, and tetrapods, which lived 105-356 Myr ago, and compare them with titin fragments from some of their modern descendants. We demonstrate that the resurrected titin molecules are rich in disulfide bonds and display high mechanical stability. These mechanochemical elements have changed over time, creating a paleomechanical trend that seems to correlate with animal body size, allowing us to estimate the sizes of extinct species. We hypothesize that mechanical adjustments in titin contributed to physiological changes that allowed the muscular development and diversity of modern tetrapods. ; Research has been supported by the Ministry of Economy and Competitiveness (MINECO) grant BIO2016-77390-R, BFU2015-71964 to R.P.-J., BIO2014-54768-P and RYC-2014-16604 to J.A-C., and CTQ2015-65320-R to D.D.S., and the European Commission grant CIG Marie Curie Reintegration program FP7-PEOPLE-2014 to R.P.-J. A.A.-C. is funded by the predoctoral program of the Basque Government. R.P.-J. and D.D.S., thank CIC nanoGUNE and the Ikerbasque Foundation for Science for financial support. CNIC is supported by the Spanish Ministry of Economy and Competitiveness (MINECO) and the Pro-CNIC Foundation and is a Severo Ochoa Center of Excellence (MINECO award SEV-2015-0505). Plasmid pQE80-(I91-32/75) 8 was a kind gift from J. Fernandez (Columbia University). We thank R. Zardoya (National Museum of Natural Sciences, Madrid) for helpful discussions and comments. The authors acknowledge technical support provided by IZO-SGI SGIker of UPV/EHU and European funding (ERDF and ESF) for the use of the Arina HPC cluster and the assistance provided by T. Mercero and E. Ogando. ; Sí
Cells remodel their structure in response to mechanical strain. However, how mechanical forces are translated into biochemical signals that coordinate the structural changes observed at the plasma membrane (PM) and the underlying cytoskeleton during mechanoadaptation is unclear. Here, we show that PM mechanoadaptation is controlled by a tension-sensing pathway composed of c-Abl tyrosine kinase and membrane curvature regulator FBP17. FBP17 is recruited to caveolae to induce the formation of caveolar rosettes. FBP17 deficient cells have reduced rosette density, lack PM tension buffering capacity under osmotic shock, and cannot adapt to mechanical strain. Mechanistically, tension is transduced to the FBP17 F-BAR domain by direct phosphorylation mediated by c-Abl, a mechanosensitive molecule. This modification inhibits FBP17 membrane bending activity and releases FBP17-controlled inhibition of mDia1-dependent stress fibers, favoring membrane adaptation to increased tension. This mechanoprotective mechanism adapts the cell to changes in mechanical tension by coupling PM and actin cytoskeleton remodeling. ; This study was supported by grants from the Spanish Ministry of Economy, Industry and Competitiveness (MINECO)/Agencia Estatal de Investigación (AEI)/European Regional Development Fund (ARDF/FEDER) "A way to make Europe" Grants (MINECO; SAF2011–25047, SAF2014–51876-R, SAF2017–83130-R, IGP-SO grant MINSEV1512–07–2016, CSD2009–0016 and BFU2016–81912-REDC), Fundació La Marató de TV3 (674/C/2013), and the Worldwide Cancer Research Foundation (♯15–0404), all to M.A.D.P. M.G.-G. is sponsored by a FPU fellowship (FPU15/03776). This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 641639. D.D.S. is supported by grants PGC2018–099321-B-I00 and RYC-2016–19590 from the Spanish Ministry of Science, Innovation and Universities. J.A.-C. acknowledges funding from MINECO grants, BIO2017–83640-P (AEI/FEDER, UE) and RYC-2014–16604. J.A.-C. and M.A.D.P. are members of the Tec4Bio consortium (ref. P2018/NMT4443; "Actividades de I+D entre Grupos de Investigación en Tecnologías," Comunidad Autónoma de Madrid/FEDER, Spain). C.H.-L. is recipient of an FPI predoctoral fellowship (BES-2015–073191). C.L. is supported by institutional grants from the Curie Institute, INSERM, and CNRS and by grants from Association Française contre les Myopathies (CAV-STRESS-MUS no. 14293), Agence Nationale de la Recherche (MOTICAV ANR-17-CE13–0020–01), the Fondation ARC pour la Recherche sur le Cancer (Programme Labellisé PGA1-RF20170205456), and programme ECOS no. C17S03. R.G.P. was supported by the National Health and Medical Research Council (NHMRC) of Australia (program grant, APP1037320 and Senior Principal Research Fellowship, 569452) and the Australian Research Council Centre of Excellence (CE140100036). We acknowledge the Australian Microscopy & Microanalysis Research Facility at the Center for Microscopy and Microanalysis at The University of Queensland. The CNIC is supported by the Instituto de Salud Carlos III (ISCIII), the Ministerio de Ciencia, Innovación y Universidades (MCNU), and the Pro CNIC Foundation and is a Severo Ochoa Center of Excellence (SEV-2015–0505). ; Sí
