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Normal modes have been used to explore the inherent flexibility of the α, β and γ subunits of F1-ATPase in isolation and as part of the α3β3γ complex. It was found that the structural plasticity of the γ and β subunits, in particular, correlates with their functions. The N and C-terminal helices forming the coiled-coil domain of the γ subunit are highly flexible in the isolated subunit, but more rigid in the α3β3γ complex due to interactions with other subunits. The globular domain of the γ subunit is structurally relatively rigid when isolated and in the α3β3γ complex; this is important for its functional role in coupling the F0 and F1 complex of ATP synthase and in inducing the conformational changes of the β subunits in synthesis. Most important, the character of the lowest-frequency modes of the βE subunit is highly correlated with the large βE→βTP transition. This holds for the C-terminal domain and the nucleotide-binding domain, which undergo significant conformational transitions in the functional cycle of F1-ATPase. This is most evident in the ligand-free βE subunit; the flexibility in the nucleotide-binding domain is reduced somewhat in the βTP subunit in the presence of Mg2+·ATP. The low-frequency modes of the α3β3γ complex show that the motions of the globular domain of the γ subunit and of the C-terminal and nucleotide binding domains of the βE subunits are coupled, in accord with their function. Overall, the normal mode analysis reveals that F1-ATPase, like other macromolecular assemblies, has the intrinsic structural flexibility required for its function encoded in its sequence and three-dimensional structure. This inherent plasticity is an essential aspect of assuring a small free energy cost for the large-scale conformational transition that occurs in molecular motors. [Copyright &y& Elsevier]

An atomic-scale mechanism of T Cell Receptor (TCR) mechanosensing of peptides in the binding groove of the peptide-major histocompatibility complex (pMHC) may inform the design of novel TCRs for immunotherapies. Using steered molecular dynamics simulations, our study demonstrates that mutations to peptides in the binding groove of the pMHC - which are known to discretely alter the T cell response to an antigen - alter the MHC conformation at equilibrium. This subsequently impacts the overall strength (duration and length) of the TCR-pMHC bond under constant load. Moreover, physiochemical features of the TCR-pMHC dynamic bond strength, such as hydrogen bonds and Lennard-Jones contacts, correlate with the immunogenic response elicited by the specific peptide in the MHC groove. Thus, formation of transient TCR-pMHC bonds is characteristic of immunogenic peptides, and steered molecular dynamics simulations can be used in the overall design strategy of TCRs for immunotherapies., (© 2022 The Author(s).)

The coronavirus disease 2019 (COVID-19), which emerged in December 2019, continues to be a serious health concern worldwide. There is an urgent need to develop effective drugs and vaccines to control the spread of this disease. In the current study, the main phytochemical compounds of Nigella sativa were screened for their binding affinity for the active site of the RNA-dependent RNA polymerase (RdRp) enzyme of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). The binding affinity was investigated using molecular docking methods, and the interaction of phytochemicals with the RdRp active site was analyzed and visualized using suitable software. Out of the nine phytochemicals of N. sativa screened in this study, a significant docking score was observed for four compounds, namely α-hederin, dithymoquinone, nigellicine, and nigellidine. Based on the findings of our study, we report that α-hederin, which was found to possess the lowest binding energy (-8.6 kcal/mol) and hence the best binding affinity, is the best inhibitor of RdRp of SARS-CoV-2, among all the compounds screened here. Our results prove that the top four potential phytochemical molecules of N. sativa , especially α-hederin, could be considered for ongoing drug development strategies against SARS-CoV-2. However, further in vitro and in vivo testing are required to confirm the findings of this study., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 The Author(s).)

The first rate-limiting enzyme of the serine synthesis pathway (SSP), phosphoglycerate dehydrogenase (PHGDH), is hyperactive in multiple tumors, which leads to the activation of SSP and promotes tumorigenesis. However, only a few inhibitors of PHGDH have been discovered to date, especially the covalent inhibitors of PHGDH. Here, we identified withangulatin A (WA), a natural small molecule, as a novel covalent inhibitor of PHGDH. Affinity-based protein profiling identified that WA could directly bind to PHGDH and inactivate the enzyme activity of PHGDH. Biolayer interferometry and LC-MS/MS analysis further demonstrated the selective covalent binding of WA to the cysteine 295 residue (Cys295) of PHGDH. With the covalent modification of Cys295, WA blocked the substrate-binding domain (SBD) of PHGDH and exerted an allosteric effect to induce PHGDH inactivation. Further studies revealed that with the inhibition of PHGDH mediated by WA, the glutathione synthesis was decreased and intracellular levels of reactive oxygen species (ROS) were elevated, leading to the inhibition of tumor proliferation. This study indicates WA as a novel PHGDH covalent inhibitor, which identifies Cys295 as a novel allosteric regulatory site of PHGDH and holds great potential in developing anti-tumor agents for targeting PHGDH., Competing Interests: The authors declare no conflicts of interest., (© 2022 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.)

Background: Lack of treatment of novel Coronavirus disease led to the search of specific antivirals that are capable to inhibit the replication of the virus. The plant kingdom has demonstrated to be an important source of new molecules with antiviral potential., Purpose: The present study aims to utilize various computational tools to identify the most eligible drug candidate that have capabilities to halt the replication of SARS-COV-2 virus by inhibiting Main protease (Mpro) enzyme., Methods: We have selected plants whose extracts have inhibitory potential against previously discovered coronaviruses. Their phytoconstituents were surveyed and a library of 100 molecules was prepared. Then, computational tools such as molecular docking, ADMET and molecular dynamic simulations were utilized to screen the compounds and evaluate them against Mpro enzyme., Results: All the phytoconstituents showed good binding affinities towards Mpro enzyme. Among them laurolitsine possesses the highest binding affinity i.e. -294.1533 kcal/mol. On ADMET analysis of best three ligands were simulated for 1.2 ns, then the stable ligand among them was further simulated for 20 ns. Results revealed that no conformational changes were observed in the laurolitsine w.r.t. protein residues and low RMSD value suggested that the Laurolitsine-protein complex was stable for 20 ns., Conclusion: Laurolitsine, an active constituent of roots of Lindera aggregata , was found to be having good ADMET profile and have capabilities to halt the activity of the enzyme. Therefore, this makes laurolitsine a good drug candidate for the treatment of COVID-19., Competing Interests: None., (© 2021 The Author(s). Published by Elsevier B.V.)

Background: Containing COVID-19 is still a global challenge. It has affected the "normal" world by targeting its economy and health sector. The effect is shifting of focus of research from life threatening diseases like cancer. Thus, we need to develop a medical solution at the earliest. The purpose of this present work was to understand the efficacy of 22 rationally screened phytochemicals from Indian medicinal plants obtained from our previous work, following drug-likeness properties, against 6 non-structural-proteins (NSP) from SARS-CoV-2., Methods: 100 ns molecular dynamics simulations were performed, and relative binding free energies were computed by MM/PBSA. Further, principal component analysis, dynamic cross correlation and hydrogen bond occupancy were analyzed to characterize protein-ligand interactions. Biological pathway enrichment analysis was also carried out to elucidate the therapeutic targets of the phytochemicals in comparison to SARS-CoV-2., Results: The potential binding modes and favourable molecular interaction profile of 9 phytochemicals, majorly from Withania somnifera with lowest free binding energies, against the SARS-CoV-2 NSP targets were identified. It was understood that phytochemicals and 2 repurposed drugs with steroidal moieties in their chemical structures formed stable interactions with the NSPs. Additionally, human target pathway analysis for SARS-CoV-2 and phytochemicals showed that cytokine mediated pathway and phosphorylation pathways were with the most significant p-value., Conclusions: To summarize this work, we suggest a global approach of targeting multiple proteins of SARS-CoV-2 with phytochemicals as a natural alternative therapy for COVID-19. We also suggest that these phytochemicals need to be tested experimentally to confirm their efficacy., Competing Interests: No potential conflict of interest was reported by the authors., (© 2020 Novel Techsciences (OPC) Private Limited.)

5-HydroxyTriptamine 2A antagonists are potential targets for treatment of various cerebrovascular and cardiovascular disorders. In this study, we have developed and performed a unique screening pipeline for filtering ZINC database compounds on the basis of similarities to known antagonists to determine novel small molecule antagonists of 5-HydroxyTriptamine 2A. The screening pipeline is based on 2D similarity, 3D dissimilarity and a combination of 2D/3D similarity. The shortlisted compounds were docked to a 5-HydroxyTriptamine 2A homology-based model, and complexes with low binding energies (287 complexes) were selected for molecular dynamics (MD) simulations in a lipid bilayer. The MD simulations of the shortlisted compounds in complex with 5-HydroxyTriptamine 2A confirmed the stability of the complexes and revealed novel interaction insights. The receptor residues S239, N343, S242, S159, Y370 and D155 predominantly participate in hydrogen bonding. π-π stacking is observed in F339, F340, F234, W151 and W336, whereas hydrophobic interactions are observed amongst V156, F339, F234, V362, V366, F340, V235, I152 and W151. The known and potential antagonists shortlisted by us have similar overlapping molecular interaction patterns. The 287 potential 5-HydroxyTriptamine 2A antagonists may be experimentally verified.

Kinesin spindle protein (KSP) belongs to the kinesin superfamily of microtubule-based motor proteins. KSP is responsible for the establishment of the bipolar mitotic spindle which mediates cell division. Inhibition of KSP expedites the blockade of the normal cell cycle during mitosis through the generation of monoastral MT arrays that finally cause apoptotic cell death. As KSP is highly expressed in proliferating/cancer cells, it has gained considerable attention as a potential drug target for cancer chemotherapy. Therefore, this study envisaged to design novel KSP inhibitors by employing computational techniques/tools such as pharmacophore modelling, virtual database screening, molecular docking and molecular dynamics. Initially, the pharmacophore models were generated from the data-set of highly potent KSP inhibitors and the pharmacophore models were validated against in house test set ligands. The validated pharmacophore model was then taken for database screening (Maybridge and ChemBridge) to yield hits, which were further filtered for their drug-likeliness. The potential hits retrieved from virtual database screening were docked using CDOCKER to identify the ligand binding landscape. The top-ranked hits obtained from molecular docking were progressed to molecular dynamics (AMBER) simulations to deduce the ligand binding affinity. This study identified MB-41570 and CB-10358 as potential hits and evaluated these experimentally using in vitro KSP ATPase inhibition assays.

The Escherichia coli uracil/H + symporter UraA, known as the representative nucleobase/cation symporter 2(NCS2) protein, gets involved in several crucial physiological processes for most living organisms on Earth, such as the uptake of nucleobases and transport of vitamin C. Some experiments proposed a working model to explain proton-coupling and uracil transporting process of UraA on the basis of the crystal structure of NCS2 protein, but the details of conformational changes remained unknown. Thus, in order to make clear conformational changes caused by the protonation and deprotonation process of some conserved proton-coupled residues, the molecular dynamics simulation was used to study the conformation of UraA complexes in different protonation states. The results demonstrated that the protonation of residue Glu241 and Glu290 resulted in the whole conformational transition from the inward-open to the outward-open state. It can be concluded that Glu290 was crucial in a network of hydrogen-bonds in the middle of the core domain involving another essential residue, mainly including tyr288 in TM8, Tyr342, Ser338 in TM12, and the network of hydrogen-bonds was the key to maintain the stability of conformation. Protonation of Glu290 affects the stability of network of H-bond and changed the domains TM3 TM10 TM12. Thus, Glu290 may play a vital role as a 'proton trigger' that affects spatial structural of amino and residues near substrate binding side leading to an outward-open conformation transition.