Structure-guided engineering of a receptor-agonist pair for inducible activation of the ABA adaptive response to drought

Strategies to activate abscisic acid (ABA) receptors and boost ABA signaling by small molecules that act as ABA receptor agonists are promising biotechnological tools to enhance plant drought tolerance. Protein structures of crop ABA receptors might require modifications to improve recognition of chemical ligands, which in turn can be optimized by structural information. Through structure-based targeted design, we have combined chemical and genetic approaches to generate an ABA receptor agonist molecule (iSB09) and engineer a CsPYL1 ABA receptor, named CsPYL15m, which efficiently binds iSB09. This optimized receptor-agonist pair leads to activation of ABA signaling and marked drought tolerance. No constitutive activation of ABA signaling and hence growth penalty was observed in transformed Arabidopsis thaliana plants. Therefore, conditional and efficient activation of ABA signaling was achieved through a chemical-genetic orthogonal approach based on iterative cycles of ligand and receptor optimization driven by the structure of ternary receptor-ligand-phosphatase complexes

C-2 Thiophenyl Tryptophan Trimers Inhibit Cellular Entry of SARS-CoV-2 through Interaction with the Viral Spike (S) Protein

26 páginas, 6 figuras, 2 tablas.Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19, by infecting cells via the interaction of its spike protein (S) with the primary cell receptor angiotensin-converting enzyme (ACE2). To search for inhibitors of this key step in viral infection, we screened an in-house library of multivalent tryptophan derivatives. Using VSV-S pseudoparticles, we identified compound 2 as a potent entry inhibitor lacking cellular toxicity. Chemical optimization of 2 rendered compounds 63 and 65, which also potently inhibited genuine SARS-CoV-2 cell entry. Thermofluor and microscale thermophoresis studies revealed their binding to S and to its isolated receptor binding domain (RBD), interfering with the interaction with ACE2. High-resolution cryoelectron microscopy structure of S, free or bound to 2, shed light on cell entry inhibition mechanisms by these compounds. Overall, this work identifies and characterizes a new class of SARS-CoV-2 entry inhibitors with clear potential for preventing and/or fighting COVID-19.Funding for this project was provided by grants from the European Commission NextGenerationEU fund (EU 2020/2094), through CSIC’s Global Health Platform (PTI Salud Global), Crue-CSIC-Santander Fondo Supera Covid-19, and CSIC grant (CSIC-COV19-082) to R.G., M.-J-P.-P., V.R., J.B., A.M., and J.-L.L. and CIBERER, Instituto de Salud Carlos III (COV20/00437) to V.R., J.B., A.M., and J.-L.L. In addition, this work was funded by grant (Covid_19-SCI) from the Generalitat Valenciana y Conselleria de Innovación, Universidades, Ciencia y Sociedad digital to R.G., and by grants PID2020-120322RB-C21 and PID2020-116880GB-I00 from the Agencia Estatal de Investigación of the Spanish Government to V.R. and J.-L.L., respectively.Peer reviewe

An Alternative Homodimerization Interface of MnmG Reveals a Conformational Dynamics that Is Essential for Its tRNA Modification Function

21 páginas, 11 figuras, 4 tablas. Material suplementario en http://dx.doi.org/10.1016/j.jmb.2018.05.035The Escherichia coli homodimeric proteins MnmE and MnmG form a functional complex, MnmEG, that modifies tRNAs using GTP, methylene-tetrahydrofolate, FAD, and glycine or ammonium. MnmE is a tetrahydrofolate- and GTP-binding protein, whereas MnmG is a FAD-binding protein with each protomer composed of the FAD-binding domain, two insertion domains, and the helical C-terminal domain. The detailed mechanism of the MnmEG-mediated reaction remains unclear partially due to incomplete structural information on the free- and substrate-bound forms of the complex. In this study, we show that MnmG can adopt in solution a dimer arrangement (form I) different from that currently considered as the only biologically active (form II). Normal mode analysis indicates that form I can oscillate in a range of open and closed conformations. Using isothermal titration calorimetry and native red electrophoresis, we show that a form-I open conformation, which can be stabilized in vitro by the formation of an interprotomer disulfide bond between the catalytic C277 residues, appears to be involved in the assembly of the MnmEG catalytic center. We also show that residues R196, D253, R436, R554 and E585 are important for the stabilization of form I and the tRNA modification function. We propose that the form I dynamics regulates the alternative access of MnmE and tRNA to the MnmG FAD active site. Finally, we show that the C-terminal region of MnmG contains a sterile alpha motif domain responsible for tRNA-protein and protein-protein interactions.This work was supported by the Spanish Ministry of Economy and Competitiveness (BFU2010-19737 and BFU2014-58673-P to M.-E.A.; BFU2016-78232-P to A.V.-C.), and Generalitat Valenciana(ACOMP/2012/065 to M.-E.A; PROMETEO/2012/061to J.B.). Funding for open access charge: [BFU2014-58673-P to M.-E.A.]Peer reviewe

Drug Discovery for Thirsty Crops

[EN] Following virtual screening and structure-based ligand optimization, researchers have developed opabactin (OP), an abscisic acid (ABA)-receptor agonist with tenfold greater in vivo activity than ABA. This new ligand surpasses previous agonists for its potency and bioactivity on staple crops. OP leads a new class of agrochemicals designed to protect crops from drought.We thank Laetitia Poidevin (IBMCP-UPV-CSIC) and Jessica Toth (UCR) for comments on the manuscript. The editor and four anonymous reviewers are also acknowledged for their constructive suggestions. We apologize to authors whose work could not be cited due to space limitations. We also acknowledge Universidad Politecnica de Valencia for the grant SP20180340 (PAID-06-18) to J.L-J. and Ministerio de Ciencia, Innovacion y Universidades for the grant RTC-2017-6019-2 to P.L.R.Lozano Juste, J.; García-Maquilón, I.; Ruiz-Partida, R.; Rodríguez Egea, PL. (2020). Drug Discovery for Thirsty Crops. Trends in Plant Science. 25(9):844-846. https://doi.org/10.1016/j.tplants.2020.07.001S84484625

Structure-Function Analysis of Escherichia coli MnmG (GidA), a Highly Conserved tRNA-Modifying Enzyme ▿ †

The MnmE-MnmG complex is involved in tRNA modification. We have determined the crystal structure of Escherichia coli MnmG at 2.4-Å resolution, mutated highly conserved residues with putative roles in flavin adenine dinucleotide (FAD) or tRNA binding and MnmE interaction, and analyzed the effects of these mutations in vivo and in vitro. Limited trypsinolysis of MnmG suggests significant conformational changes upon FAD binding

C‑2 Thiophenyl Tryptophan Trimers Inhibit Cellular Entry of SARS-CoV‑2 through Interaction with the Viral Spike (S) Protein

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19, by infecting cells via the interaction of its spike protein (S) with the primary cell receptor angiotensin-converting enzyme (ACE2). To search for inhibitors of this key step in viral infection, we screened an in-house library of multivalent tryptophan derivatives. Using VSV-S pseudoparticles, we identified compound 2 as a potent entry inhibitor lacking cellular toxicity. Chemical optimization of 2 rendered compounds 63 and 65, which also potently inhibited genuine SARS-CoV-2 cell entry. Thermofluor and microscale thermophoresis studies revealed their binding to S and to its isolated receptor binding domain (RBD), interfering with the interaction with ACE2. High-resolution cryoelectron microscopy structure of S, free or bound to 2, shed light on cell entry inhibition mechanisms by these compounds. Overall, this work identifies and characterizes a new class of SARS-CoV-2 entry inhibitors with clear potential for preventing and/or fighting COVID-19