Design Of Potent Inhibitors Research Articles

Development of an invitro screening assay for PIP5K1α lipid kinase and identification of potent inhibitors.

The human phosphatidylinositol 4-phosphate 5-kinase type I α (hPIP5K1α) participates in the phosphoinositide-3-kinase/protein kinase B/mammalian target of rapamycin signaling pathway. Despite the evidence that hPIP5K1α plays a role in the development of prostate cancer (PCa), only one inhibitor is known to date. With the aim of identifying new inhibitors, a nonradiometric assay for measurement of the hPIP5K1α enzyme activity was developed. The assay is based on the separation of the fluorescently labeled substrate phosphatidylinositol-4-phosphate (PI(4)P) and the resulting product phosphatidylinositol-4,5-bisphosphate (PIP2 ) by capillary electrophoresis (CE). Furthermore, an inactive mutant K261A of hPIP5K1α was generated by site-directed mutagenesis and used as a control. Michaelis-Menten analysis revealed a Km value of 21.6µm and Vmax of 0.65pmol·min-1 for the cosubstrate ATP. The average Z' value was determined to be 0.86, indicating a high reliability of the assay. An insilico screening of an in-house compound library was performed employing the crystal structure of zebrafish PIP5K1α. By applying this strategy, three compounds with a 2-amino-3-cyano-4H-pyranobenzoquinone scaffold were identified and tested using the CE-based assay. These compounds inhibited hPIP5K1α to >90% at a concentration of 50µm. Subsequently, the inhibitory activity of all compounds with a pyranobenzoquinone scaffold (29) was tested on hPIP5K1α. Compound 4-(2-amino-3-cyano-6-hydroxy-5,8-dioxo-7-undecyl-5,8-dihydro-4H-chromen-4-yl)benzoic acid appeared to be the most potent inhibitor of hPIP5K1α identified so far with an IC50 value of 1.55µm, exhibiting a substrate-competitive mode of action. The effects of this compound on cell viability and the induction of apoptosis were investigated in LNCaP, DU145, and PC3 PCa cells.

Identification of potential inhibitors against pathogenic missense mutations of PMM2 using a structure-based virtual screening approach

The autosomal recessive phosphomannomutase 2-congenital disorder of glycosylation (PMM2-CDG) is characterized by defective functioning of the PMM2 enzyme, which is necessary for the conversion of mannose-6-phosphate into mannose-1-phosphate. Here, a computational pipeline was drawn to identify the most significant mutations, and further, we used a virtual screening approach to identify a new lead compound to treat the identified significant mutations. We searched for missense mutation data related to PMM2-CDG in HGMD®, UniProt, and ClinVar. Our search yielded a total of 103 mutations, of which 91 are missense mutations. The D65Y, I132N, I132T, and F183S mutations were classified as deleterious, destabilizing, and altering the biophysical properties using the PredictSNP, iStable, and Align GVGD in silico prediction tools. Additionally, we applied a multistep protocol to screen for an alternative lead compound to the existing CID2876053 (1-(3-chlorophenyl)-3,3-bis(pyridine-2-yl)urea) with affinity to these identified significant mutants. Two compounds, CHEMBL1491007 (6-chloro-4-phenyl-3-(4-pyridin-2-ylpiperazin-1-yl)-1H-quinolin-2-one) and CHEMBL3653029 (5-chloro-4-[6-[(3-fluorophenyl)methylamino]pyridin-2-yl]-N-(piperidin-4-ylmethyl)pyridin-2-amine), exhibited the highest binding affinity with the selected mutants and were chosen for further analysis. Through molecular docking, molecular dynamics simulation, and MMPBSA analysis, we found that the known compound, i.e. CID2876053, has stronger interaction with the D65Y mutant. The newly identified lead compound CHEMBL1491007 showed stronger interaction with the I132N and I132T mutants, whereas the most deleterious mutant, F183S, showed stronger interaction with CHEMBL3653029. This study is expected to aid in the field of precision medicine, and further to in vivo and in vitro analysis of these lead compounds might shed light on the treatment of PMM2-CDG. Communicated by Ramaswamy H. Sarma

In Silico Identification of Potential Inhibitors of the Main Protease of SERS-CoV-2 Using Combined Ligand-based and Structure-based Drug Design approach

Objectives: The outbreak of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2) remains a serious global threat At the time of writing, there are no specific therapeutic agents or vaccines to combat this disease This study was designed to identify the SARS-CoV-2 main protease inhibitors using drug molecule information retrieved from DrugBank 5 0 (Wishart et al ) Methods: A set of common pharmacophores were generated from a series of 22 known SARS-CoV inhibitors The best pharmacophore used for virtual screening (VS) of DrugBank using the Phase module followed by structure-based virtual screening (VS) using Glide (Release 2020-1;Schrodinger LLC, New York, NY, USA) with SARS-CoV-2 main protease and 50 ns molecular dynamics (MD) simulation studies Results: Six hits were selected based on the fitness score, extra-precision Glide score, and binding affinity with the main protease (Mpro) The predicted inhibitor constant (Ki) values of the 3 best hits, DB03777, DB06834, and DB07456, were 0 8176, 0 2148, and 0 1006 mu M, respectively An MD simulation of DB07456 and DB13592 with the Mpro demonstrated stable protein-ligand complexes Conclusion: The selected inhibitors displayed a similar type of binding interaction with co-ligands and remdesivir, and the predicted Ki values of 2 inhibitors were found to be superior to remdesivir These selected hits may be used for further in vitro and in vivo studies against the SARS- CoV-2 Mpro

Deciphering molecular mechanism behind conformational change of the São Paolo metallo-β-lactamase 1 by using enhanced sampling

The São Paolo metallo-β-lactamase-1 (SPM-1) plays an important role in drug resistance of β-lactam antibiotics and bindings of zinc ions produce significant effect on the conformations of SPM-1. Thus, it is of significance for understanding function of SPM-1 to probe the conformational changes of SPM-1 induced by bindings of zinc ions. Because replica-exchange molecular dynamics (REMD) simulations can efficiently improve conformational samplings of proteins, REMD and normal mode analysis (NMA) were performed on three systems, including SPM-1 with non-zinc ions, single zinc ion and double zinc ions, to decipher molecular mechanism of conformational changes for SPM-1. The results suggest that binding of double zinc ions induces a closed state of SPM-1, while SPM-1 with binding of non-zinc and single zinc ion mainly exists as an open conformation. The analysis of interaction network between residues was carried out by using the program Ring 2.0. The results show that binding of double zinc ions highly enhances the stability of the π-π interaction network consisting of F60, Y61, F82, F152, Y153 and Y226, two hydrogen bonds between E83 and R161 as well as the salt bridge interaction between E151 and K159 compared to the SPM-1 with non-zinc or single zinc ion, which better stabilizes the closed conformation of SPM-1. Thus, the closed conformation of SPM-1 induced by bindings of double zinc ions is important in catalysis and determining inhibitor selectivity. Meanwhile, this work may provide useful theoretical hints for design of potent inhibitors toward drug resistance of β-lactam antibiotics.Communicated by Ramaswamy H. Sarma.

Computational and Pharmacogenomic Insights on Hypertension Treatment: Rational Drug Design and Optimization Strategies.

Hypertension is a prevalent cardiovascular complication caused by genetic and nongenetic factors. Blood pressure (BP) management is difficult because most patients become resistant to monotherapy soon after treatment initiation. Although many antihypertensive drugs are available, some patients do not respond to multiple drugs. Identification of personalized antihypertensive treatments is a key for better BP management. This review aimed to elucidate aspects of rational drug design and other methods to develop better hypertension management. Among hypertension-related signaling mechanisms, the renin-angiotensin-aldosterone system is the leading genetic target for hypertension treatment. Identifying a single drug that acts on multiple targets is an emerging strategy for hypertension treatment, and could be achieved by discovering new drug targets with less mutated and highly conserved regions. Extending pharmacogenomics research to include patients with hypertension receiving multiple antihypertensive drugs could help identify the genetic markers of hypertension. However, available evidence on the role of pharmacogenomics in hypertension is limited and primarily focused on candidate genes. Studies on hypertension pharmacogenomics aim to identify the genetic causes of response variations to antihypertensive drugs. Genetic association studies have identified single nucleotide polymorphisms affecting drug responses. To understand how genetic traits alter drug responses, computational screening of mutagenesis can be utilized to observe drug response variations at the protein level, which can help identify new inhibitors and drug targets to manage hypertension. Rational drug design facilitates the discovery and design of potent inhibitors. However, further research and clinical validation are required before novel inhibitors can be clinically used as antihypertensive therapies.

Molecular mechanism of inhibitor bindings to bromodomain-containing protein 9 explored based on molecular dynamics simulations and calculations of binding free energies

ABSTRACTRecently, bromodomain-containing protein 9 (BRD9) has been a prospective therapeutic target for anticancer drug design. Molecular dynamics (MD) simulations combined with molecular mechanics generalized Born surface area (MM-GBSA) method were adopted to explore binding modes of three inhibitors (5SW, 5U2, and 5U6) to BRD9 and identify the hot spot of the inhibitor-BRD9 binding. The results indicate that the inhibitor 5SW has the strongest binding ability to BRD9 among the current three inhibitors. Furthermore, the rank of the binding free energies predicted by MM-GBSA approach agrees with that determined by the experimental values. In addition, inhibitor-residue interactions were computed by using residue-based free-energy decomposition method and the results suggest that residue His42 produces the CH-H interactions, residues Asn100, Ile53 and Val49 produce the CH- interactions with three inhibitors and Tyr106, Phe45 and Phe44 generate the π-π interactions with inhibitors. Notably, the residue Asn140 forms hydrogen bonding interactions with three inhibitors. This research is expected to provide useful molecular basis and dynamics information at atomic levels for the design of potent inhibitors inhibiting the activity of BRD9.

Computational study on cross-talking cancer signalling mechanism of ring finger protein 146, AXIN and Tankyrase protein complex

Cancer is distinguished by uncontrolled cell growth and it is regulated by several environmental and genetic factors. The Wnt β-Catenin signaling pathway has been considered as the most significant colon cancer-targeted pathway. AXIN plays a major regulatory role in the Wnt signaling mechanism. The AXIN after PARsylated by TNKS is ubiqutinated by RNF146 through its WWE domain that leads to degradation of AXIN protein. Several studies have been proposed highlighting the inhibition of the PARsylation mechanism that mediates the degradation of AXIN and improves β-catenin stability. The present study focused on the identification of potential inhibitors for the inhibition of RNF146-TNKS complex through identifying potential RNF146 inhibitors to prevent ubiquitination of AXIN, further to confirm the regulatory role and inhibition mechanism of RNF146-AXIN and RNF146-TNKS. The docked complex was then evaluated using various computational analysis. Molecular interactions analysis was performed to observe the interacting residues between the protein complex. The compounds from various databases were docked with the RNF146 and complex proteins. Both the protein complex and ligand were analyzed for the confirmation of structural stability using molecular dynamics simulations. Selected compounds’ atomic configuration and electron profile were analyzed through DFT calculations and ADME/T (Physico-chemical) properties. As a result, we found several common lead compounds for RNF146, TNKS protein inhibition. Therefore, the docked compounds may act as a better antagonist molecule for RNF146, TNKS and associated signaling molecules. Further, experimental validations are required to prove the potency of the identified compounds.Communicated by Ramaswamy H. Sarma

Identification of potential inhibitors for HCV NS5b of genotype 4a by combining dynamic simulation, protein–ligand interaction fingerprint, 3D pharmacophore, docking and 3D QSAR

HCV NS5B polymerase has been one of the most attractive targets for developing new drugs for HCV infection and many drugs were successfully developed, but all of them were designed for targeting Hepatitis C Virus genotype 1 (HCV GT1). Hepatitis C virus genotype 4a (HCV GT4a) dominant in Egypt has paid less attention. Here, we describe our protocol of virtual screening in identification of novel potential potent inhibitors for HCV NS5B polymerase of GT4a using homology modeling, protein–ligand interaction fingerprint (PLIF), docking, pharmacophore, and 3D CoMFA quantitative structure activity relationship (QSAR). Firstly, a high-quality 3D model of HCV NS5B polymerase of GT4a was constructed using crystal structure of HCV NS5B polymerase of GT1 (PDB ID: 3hkw) as a template. Then, both the model and the template were simulated to compare conformational stability. PLIF was generated using five crystal structures of HCV NS5B (PDB ID: 4mia, 4mib, 4mk9, 4mka, and 4mkb), which revealed the most important residues and their interactions with the co-crystalized ligands. After that, a 3D pharmacophore model was developed from the generated PLIF data and then used as a screening filter for 17000328 drug-like zinc database compounds. 900 compounds passed the pharmacophore filter and entered the docking-based virtual screening stage. Finally, a 3D CoMFA QSAR was developed using 42 compounds as a training and 19 compounds as a test set. The 3D CoMFA QSAR was used to design and screen some potential inhibitors, these compounds were further evaluated by the docking stage. The highest ranked five hits from docking result (compounds (p1–p4) and compound q1) were selected for further analysis.Communicated by Ramaswamy H. Sarma

In silico-guided identification of potential inhibitors against β2m aggregation in dialysis-related amyloidosis

In dialysis-related amyloidosis (DRA), misfolding of β2-microglobulin (β2m) leads to amyloid fibril deposition mainly in the skeletal joints seriously affecting their functionality. The identification and characterization of small-molecules that bind β2m and possibly inhibit its aggregation remain unexplored. In the present study, a ligand-based virtual screening approach and molecular dynamics (MD) simulations were employed to explore potent small-molecule inhibitors against β2m aggregation. The compounds were screened from various small-molecule databases by applying ligand-based virtual screening with rifamycin SV (RSV) as a reference compound. The molecular docking analysis was performed to filter out lead compounds with a higher binding affinity than RSV from a library of ∼800 compounds. Three compounds, ChEBI68321 (C1), ChEMBL360190 (C2) and ZINC3091144 (C3), displaying excellent binding free energies of –51.29, –36.51 and –34.36 kcal/mol, respectively, with β2m were subjected to MD simulations to get insights into the binding locations, key interactions and structural stability of the β2m-ligand complexes. The hydrogen bond analysis highlight higher structural stability and reduced flexibility of the loop regions of β2m in presence of C1, C2 and C3. The integrated computational approach employed in the present study identify promising lead compounds against β2m aggregation in DRA.Abbreviationsβ2mβ2-microglobulin3Dthree dimensionalADAlzheimer’s diseaseADTAutoDock ToolsDRADialysis-related amyloidosisDSSPdictionary of secondary structure of proteinsFELfree energy landscapeGROMACSGROningen MAchine for Chemical SimulationsLGALamarckian Genetic AlgorithmLINCSLINear Constraint SolverMCmain chainMDmolecular dynamicsMHC–Imajor histocompatibility complex class IMM–PBSAmolecular mechanics Poisson–Boltzmann surface areaPMEnanometer (nm); particle mesh ewaldPCAprincipal component analysisPDBprotein data bankRgradius–of–gyrationRSVrifamycin SVRMSDroot–mean–square deviationRMSFroot–mean–square fluctuationSCside chainSPCsimple point chargeSASASolvent accessible surface areaVMDvisual molecular dynamicsCommunicated by Ramaswamy H. Sarma

Structure Based Identification of Potential Inhibitors of NS3 Protein of Zika Virus

Background:The re-emerging Zika virus has posed a serious threat to human health due to its association with the neurological disorders. The NS3 protein of Zika virus plays a pivotal role in the genome replication and thus may prove to be a critical target for the drug designing studies.Objective:The present study was conceptualized to analyze the crystal structure of NS3 protein of Zika virus followed by the identification of it’s potential inhibitors.Methods:Crystal structure of the NS3 protein was evaluated in detail. Docking of the NS3 protein was done with 130 different ligands including dengue virus inhibitors and their similar compounds along with some approved drugs. The drug likeliness properties were checked for non drug compounds.Results:Structural analysis of the NS3 protein revealed three important sites namely ATP- and RNAbinding sites as well as a central cavity. The selected ten ligands (ZINC05487635, ZINC0092398, ZINC13345444, 4-methoxyphenyl 4-chloro-3-nitrobenzoate, Luteolin, Ivermectin, Suramin, Dasatinib, Panduratin A, and ARDP0009) showed a higher binding affinity for the NS3 protein and good drug likeliness properties.Conclusion:These inhibitors could possibly act as potential lead molecules for future drug designing studies. Our present computational data is envisaged to be useful for gathering experimental evidences towards the development of potential therapeutic molecules against this arthropod mediated pathogen.

Identification of Potent Inhibitors against Potential Drug Target for Schizophrenia Trough Virtual Screening Approach

Identification of Potent Inhibitors against Potential Drug Target for Schizophrenia Trough Virtual Screening Approach

Identification of Potent Inhibitors against NS3 Protease of West Nile Virus using in Silico Approaches

Identification of Potent Inhibitors against NS3 Protease of West Nile Virus using in Silico Approaches

The Effect of Sulfur Atom Substitution on Organophosphorus Inhibitors of Butyrylcholinesterase

Butyrylcholinesterase (BuChE) is an enzyme that is highly upregulated in the pathogenesis of Alzheimer's Disease (AD) and contributes to the symptomatic cognitive decline through the hydrolysis of the neurotransmitter, acetylcholine. We have recently developed BuChE-specific, reversible organophosphorus inhibitors in which two phosphates are linked by an alkyl chain. Subsequent changes in drug design led to a better and smaller inhibition constant (Ki) by replacing the two oxygen atoms in the linker with sulfur atoms. Therefore, it is hypothesized that the position as well as an increase in the number of sulfur substitutions around the phosphorus atom will lead to a more potent inhibitor design. To evaluate the effects of these sulfur atoms on inhibition, dibutyl hexyl phosphate will be used as a scaffold for making a library of potential compounds, each with different number and location of substitutions. The reversibility of inhibition and the specificity is determined through an in vitro competition assay by incubating BuChE with inhibitor for various time intervals and then doping in butyrylthiocholine, a molecule that can be hydrolyzed by BuChE; the hydrolyzed product will react with Ellman's reagent to give an absorbance reading at 412 nanometers. Preliminary data for a single sulfur atom substitution on the hexyl chain shows about a 50-fold decrease in Ki compared to the control that has all oxygen atoms (1.3 versus 50 μM, respectively). When assayed against acetylcholinesterase, no inhibition was observed. Analogs bearing a thiophosphoryl group (P=S) show decreased inhibition compared to the phosphoryl (P=O) compounds (1.3 versus 3.4 μM). Despite the difference in location, a single substitution has led to an irreversible, yet selective inhibition of BuChE. The insight from this study will give guidance towards the rational design of better inhibitors of BuChE that can potentially decelerate the symptomatic progression of AD. Support or Funding Information This project is supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number R25GM071638. The content is solely the responsibility of the author and does not necessarily represent the official views of the National Institutes of Health. Library of phosphate and phosphorothioate compounds that will be evaluated for selective inhibition of butyrylcholinesterase This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Identification of Potential Inhibitors from Pyriproxyfen with Insecticidal Activity by Virtual Screening.

Aedes aegypti is the main vector of dengue fever transmission, yellow fever, Zika, and chikungunya in tropical and subtropical regions and it is considered to cause health risks to millions of people in the world. In this study, we search to obtain new molecules with insecticidal potential against Ae. aegypti via virtual screening. Pyriproxyfen was chosen as a template compound to search molecules in the database Zinc_Natural_Stock (ZNSt) with structural similarity using ROCS (rapid overlay of chemical structures) and EON (electrostatic similarity) software, and in the final search, the top 100 were selected. Subsequently, in silico pharmacokinetic and toxicological properties were determined resulting in a total of 14 molecules, and these were submitted to the PASS online server for the prediction of biological insecticide and acetylcholinesterase activities, and only two selected molecules followed for the molecular docking study to evaluate the binding free energy and interaction mode. After these procedures were performed, toxicity risk assessment such as LD50 values in mg/kg and toxicity class using the PROTOX online server, were undertaken. Molecule ZINC00001624 presented potential for inhibition for the acetylcholinesterase enzyme (insect and human) with a binding affinity value of −10.5 and −10.3 kcal/mol, respectively. The interaction with the juvenile hormone was −11.4 kcal/mol for the molecule ZINC00001021. Molecules ZINC00001021 and ZINC00001624 had excellent predictions in all the steps of the study and may be indicated as the most promising molecules resulting from the virtual screening of new insecticidal agents.

Virtual screening and docking of lead like molecules against Glutathione-S-Transferase protein from Brugia malayi.

Glutathione-S-transferase(s) (GST) is an important chemotherapeutic target in lymphatic filarasis caused by Brugia malayi and Wuchereria bancrofti. It has been playing an important role as major detoxification enzyme and help in intracellular transportation of hydrophobic substrates. Therefore, it is of interest to screen GST from Brugia malayi with millions of known ligands at the ZINC database using AUTODOCK for the identification of potential inhibitors with improved binding characteristics. We report two potent inhibitors ZINC00179016 and ZINC08385519 which are the molecules of pyrrolidinedione and benzimidazole families respectively as potential inhibitors of GST from Brugia malayi with suitable binding properties.

Discovery of Potent Inhibitors for the Inhibition of Dengue Envelope Protein: An In Silico Approach.

Dengue fever, a major public health problem in the tropical and sub-tropical countries caused by the infection of Dengue virus transmitted by the anthropod vectors. The dengue virus infection is represented as the "Neglected Tropical Diseases" by the world health organization. The structural protein E binds to the receptor on the host cell surface during infection and the binding directs to the endocytic pathway. The conformational change of the envelope protein helps to infuse the viral lipid membrane and delivers the viral genome into the cytosol. No specific treatments are available till date and development of the vaccine for the DENV is challenging due to the immunization and longlasting protection against all four serotypes. Hence, identification of potent inhibitors would overlay the therapeutics against the mediated diseases. Our study focuses on developing the novel potent inhibitors to inhibit the viral attachment and membrane fusion of the Dengue virus Envelope protein. The crystal structure of Dengue Envelope protein has been retrieved from the protein data bank and optimized through Schrödinger. The structure-based virtual screening based on the cocrystallised ligand has been carried out with the small molecule libraries, and based on the docking score, interaction and energy value best complexes were selected. The selected complexes were further taken forward for the conformational stability analysis through Molecular dynamics simulation. Around 55 molecules from the three databases were identified as potential binders to the envelope protein and the docking studies revealed that the top compounds possess strong interaction with the good energies. The Molecular electrostatic surface potential of the top five compounds states that the interactions were observed mostly in the electropositive region. Finally, the best 5 compounds carried further for molecular dynamics simulations exposed that they were highly stable and no loss of interactions was observed between those complexes. Hence, from the results, it is evident that the compounds DB00179, Quercetin, Silymarin, Dapagliflozlin and Fisetin could be novel and potent candidates to inhibit the DENV envelope protein.

Electrostatic interaction-mediated conformational changes of adipocyte fatty acid binding protein probed by molecular dynamics simulation

Adipocyte fatty acid binding protein (A-FABP) is a potential drug target for treatment of diabetes, obesity and atherosclerosis. Molecular dynamics (MD) simulations, principal component (PC) analysis and binding free energy calculations were combined to probe effect of electrostatic interactions of residues R78, R106 and R126 with inhibitors ZGB, ZGC and IBP on structural stability of three inhibitor/A-FABP complexes. The results indicate that mutation R126A produces significant influence on polar interactions of three inhibitors with A-FABP and these interactions are main force for driving the conformational change of A-FABP. Analyses on hydrogen bond interactions show that the decrease in hydrogen bonding interactions of residues R126 and Y128 with three inhibitors and the increase in that of K58 with inhibitors ZGC and IBP in the R126A mutated systems mostly regulate the conformational changes of A-FABP. This work shows that R126A can generate a significant perturbation on structural stability of A-FABP, which implies that R126 is of significance in inhibitor bindings. We expect that this study can provide a theoretical guidance for design of potent inhibitors targeting A-FABP.Communicated by Ramaswamy H. Sarma

Exploring the flap dynamics of the South African HIV subtype C protease in presence of FDA-approved inhibitors: MD study.

HIV-1 protease (HIV PR) is considered as one of the most attractive targets for the treatment of HIV and the impact of flap dynamics of HIV PR on the binding affinities of protease inhibitors (PIs) is a crucial ongoing research field. Recently, our research group evaluated the binding affinities of different FDA approved PIs against the South African HIV-1 subtype C (C-SA) protease (PR). The CSA-HIV PR displayed weaker binding affinity for most of the clinical PIs compared to HIV-1 B subtype for West and Central Europe, the Americas. In the current work, the flap dynamics of four different systems of HIV-1 C-SA PR complexed to FDA approved second generation PIs and its impact on binding was explored over the molecular dynamic trajectories. It was observed that the interactions of the selected drugs with the binding site residues of the protease may not be the major contributor for affinity towards PIs. Various post-MD analyses were performed, also entropic contributions, solvation free energies and hydrophobic core formation interactions were studied to assess how the flap dynamics of C-SA PR which is affected by such factors. From these contributions, large van der Waals interactions and low solvation free energies were found to be major factors for the higher activity of ATV against C-SA HIV PR. Furthermore, a comparatively stable hydrophobic core may be responsible for higher stability of the PR flaps of the ATV complex. The outcome of this study provides significant guidance to how the flap dynamics of C-SA PR is affected by various factors as a result of the binding affinity of various protease inhibitors. It will also assist with the design of potent inhibitors against C-SA HIV PR that apart from binding in the active site of PR can interacts with the flaps to prevent opening of the flaps resulting in inactivation of the protease.

Mechanism of imipenem resistance in metallo-β-lactamases expressing pathogenic bacterial spp. and identification of potential inhibitors: An in silico approach.

The World Health Organization reports that millions of people around the world are infected with antibiotic-resistant bacteria. Such resistance is more common in Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae strains because of the expression of the metallo-β-lactamases (MBLs) namely Imipenemase (IMP)-1, IMP-2, New Delhi metallo-β-lactamases-, Verona imipenemase (VIM)-4, VIM-5, and VIM-7. We did an in silico analysis to understand the resistance mechanism of imipenem at the structural level. Our modeling studies reveal that the VIM-4-imipenem complex has highest binding energy and forms a stable complex as indicated by a consensus score (C-score) value of 5.44. The intense interaction between the substrate and the β-lactamases leads to the increased hydrolysis of the substrate resulting in rapid hydrolysis of the antibiotic imipenem by VIM-4. Virtual screening of compounds from the ZINC database targeting VIM-4 was done, and we found compound ZINC44608383 as the high binding energy compound with the C-score value of 5.58. This compound could be exploited for inhibitor design and development. The current study helps us to understand the resistance mechanism of imipenem in MBL-expressing strains. Also, we have identified a probable inhibitor for VIM-4. We believe that our results will be useful for researchers in designing potent inhibitors for VIM-4.

Identification of potential inhibitors against nuclear Dam1 complex subunit Ask1 of Candida albicans using virtual screening and MD simulations

Identification of hit compounds against specific target form the starting point for a drug discovery program. A consistent decline of new chemical entities (NCEs) in recent years prompted a challenge to explore newer approaches to discover potential hit compounds that in turn can be converted into leads, and ultimately drug with desired therapeutic efficacy. The vast amount of omics and activity data available in public databases offers an opportunity to identify novel targets and their potential inhibitors. State of the art in silico methods viz., clustering of compounds, virtual screening, molecular docking, MD simulations and MMPBSA calculations were employed in a pipeline to identify potential ‘hits’ against those targets as well whose structures, as of now, could only predict through threading approaches. In the present work, we have started from scratch, amino acid sequence of target and compounds retrieved from PubChem compound database, modeled it in such a way that led to the identification of possible inhibitors of Dam1 complex subunit Ask1 of Candida albicans. We also propose a ligand based binding site determination approach. We have identified potential inhibitors of Ask1 subunit of a Dam1 complex of C. albicans, which is required to prevent precocious spindle elongation in pre-mitotic phases. The proposed scheme may aid to find virtually potential inhibitors of other unique targets against candida.