HHV-5 epitope: A potential vaccine candidate with high antigenicity and large coverage

Outbreak of Human Herpes virus-5 (HHV-5) infection in emerging countries has raised worldwide health concern owing to prevalence of congenital impairments and life threatening consequences in immunocompromised individuals. Thus, there lies an impending need to develop vaccine against HHV-5. HHV-5 enters into host cells with the help of necessary components glycoprotein B (gB) and H/L. In this study, the conformational linear B-cell and T-cell epitopes for gB of HHV-5 have been predicted using conformational approaches, for their possible collective use as vaccine candidates. We examined epitope's interactions with major histocompatibility complexes using molecular docking and also investigated their stable binding with specific toll like receptor-2 (TLR2), present on host cells during HHV-5 infection. Predicted MHC-I epitope 'LVAIAVVII' with high antigenicity and large coverage of HLA alleles was found to superimpose on MHC-II epitope (Rank 1) and was also identified to be the core sequence of putative B cell epitope 'ILVAIAVVIITYLI'. Resulting epitope was found to have consistent interaction with TLR2 during long term (100 ns) MD run. We also validated this nonamer epitope for its dissimilarity with human genome and high population coverage, suggesting it to be a potential vaccine candidate with higher coverage for both the MHC alleles of Indian population. Communicated by Ramaswamy H. Sarma.

Dynamics of Dof domain-DNA interaction in wheat: Insights from atomistic simulations and free energy landscape

DNA-binding one zinc finger protein (Dof) is a plant-specific transcription factor involved in numerous biological processes. In the current study, the plausible mechanism underlying Dof domain-DNA interaction in wheat was investigated using extensive molecular dynamics (MD) simulations analysis. We depicted that one key residue Lys29, possessing the ability to disturb the interaction between Dof domain-DNA upon substitution to Arg29. Frequent conformational changes were observed in Lys29Arg (K29R)-DNA complex during the entire MD simulation period, which significantly altered the interactions, thereby indicating the importance of Lys29 in complex stability. Principal component analysis and free energy landscape results also suggested strong affinity between wild-type Dof domain and DNA due to restricted atomic movement. Our study not only substantiates the structural and mechanistic insights of Dof transcription factor but also provides new avenues toward employment of these key amino acid residues in genetic engineering for development of abiotic stress tolerance crop plant.

Drug targeted virtual screening and molecular dynamics of LipU protein of Mycobacterium tuberculosis and Mycobacterium leprae

The lipolytic protein LipU was conserved in mycobacterium sp. including M. tuberculosis (MTB LipU) and M. leprae (MLP LipU). The MTB LipU was identified in extracellular fraction and was reported to be essential for the survival of mycobacterium. Therefore to address the problem of drug resistance in pathogen, LipU was selected as a drug target and the viability of finding out some FDA approved drugs as LipU inhibitors in both the cases was explored. Three-dimensional (3D) model structures of MTB LipU and MLP LipU were generated and stabilized through molecular dynamics (MD). FDA approved drugs were screened against these proteins. The result showed that the top-scoring compounds for MTB LipU were Diosmin, Acarbose and Ouabain with the Glide XP score of -12.8, -11.9 and -11.7 kcal/mol, respectively, whereas for MLP LipU protein, Digoxin (-9.2 kcal/mol), Indinavir (-8.2 kcal/mol) and Travoprost (-8.2 kcal/mol) showed highest affinity. These drugs remained bound in the active site pocket of MTB LipU and MLP LipU structure and interaction grew stronger after dynamics. RMSD, RMSF and Rg were found to be persistent throughout the simulation period. Hydrogen bonds along with large number of hydrophobic interactions stabilized the complex structures. Binding free energies obtained through Prime/MM-GBSA were found in the significant range from -63.85 kcal/mol to -34.57 kcal/mol for MTB LipU and -71.33 kcal/mol to -23.91 kcal/mol for MLP LipU. The report suggested high probability of these drugs to demolish the LipU activity and could be probable drug candidates to combat TB and leprosy disease.

Synergistic approaches unraveling regulation and aggregation of intrinsically disordered β-amyloids implicated in Alzheimer's disease

Alzheimer's disease is a severe brain illness that causes vast numbers of nerve cells in the brain to die, driven by the production and deposition of amyloid beta (Aβ) peptides. Intrinsically disordered proteins (IDPs) generally lack stable structures and are abundant in nature. Aβ peptide is a well-known IDP with a wide range of oligomeric forms. Dysfunctions in Aβ lead to oligomerization, formation of fibrils, and neurodegenerative disorders or other forms of dementia. In this study, we used replica exchange molecular dynamics (REMD) to elucidate the roles of different osmolytes, particularly urea and trimethylamine N-oxide (TMAO), to study shifts in IDP populations. REMD samples the conformational space efficiently and at physiologically relevant temperatures, compared to conventional molecular dynamics that sample at a constant temperature. Urea is known to minimize the aggregation process, while TMAO is beneficial for its stabilizing action. The two osmolytes displayed characteristic effects on Aβ peptides and resulted in progressive modulation of conformations. The present study underlines the hypothesis of "modulation of conformational ensembles" to explain the regulation and aggregation of IDPs.

Molecular dynamics simulations revealed structural differences among WRKY domain-DNA interaction in barley (Hordeum vulgare)

Background

The WRKY transcription factors are a class of DNA-binding proteins involved in diverse plant processes play critical roles in response to abiotic and biotic stresses. Genome-wide divergence analysis of WRKY gene family in Hordeum vulgare provided a framework for molecular evolution and functional roles. So far, the crystal structure of WRKY from barley has not been resolved; moreover, knowledge of the three-dimensional structure of WRKY domain is pre-requisites for exploring the protein-DNA recognition mechanisms. Homology modelling based approach was used to generate structures for WRKY DNA binding domain (DBD) and its variants using AtWRKY1 as a template. Finally, the stability and conformational changes of the generated model in unbound and bound form was examined through atomistic molecular dynamics (MD) simulations for 100 ns time period.

Results

In this study, we investigated the comparative binding pattern of WRKY domain and its variants with W-box cis-regulatory element using molecular docking and dynamics (MD) simulations assays. The atomic insight into WRKY domain exhibited significant variation in the intermolecular hydrogen bonding pattern, leading to the structural anomalies in the variant type and differences in the DNA-binding specificities. Based on the MD analysis, residual contribution and interaction contour, wild-type WRKY (HvWRKY46) were found to interact with DNA through highly conserved heptapeptide in the pre- and post-MD simulated complexes, whereas heptapeptide interaction with DNA was missing in variants (I and II) in post-MD complexes. Consequently, through principal component analysis, wild-type WRKY was also found to be more stable by obscuring a reduced conformational space than the variant I (HvWRKY34). Lastly, high binding free energy for wild-type and variant II allowed us to conclude that wild-type WRKY-DNA complex was more stable relative to variants I.

Conclusions

The results of our study revealed complete dynamic and structural information about WRKY domain-DNA interactions. However, no structure base information reported to date for WRKY variants and their mechanism of interaction with DNA. Our findings highlighted the importance of selecting a sequence to generate newer transgenic plants that would be increasingly tolerance to stress conditions.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4506-3) contains supplementary material, which is available to authorized users.

Insight into the inhibitor discrimination by FLT3 F691L

Fms-like tyrosine kinase 3 (FLT3) belongs to the receptor tyrosine kinase family and expressed in hematopoietic progenitor cells. FLT3 gene mutations are reported in ~30% of acute myeloid leukemia cases. FLT3 kinase domain mutation F691L is one of the common causes of acquired resistance to the FLT3 inhibitors including quizartinib. MZH29 and crenolanib were previously reported to inhibit FLT3 F691L. However, crenolanib was reported for the moderate inhibition. We found that Glu661and Asp829 were the most significant residues to target the FLT3 F691L which contribute most significantly to the binding energy with MZH29 and crenolanib. These interactions were found absent with quizartinib. Further free energy landscape analysis revealed that FLT3 F691L bound to MZH29 and crenolanib was more stable as compared to quizartinib.

Structural investigations on mechanism of lapatinib resistance caused by HER-2 mutants

HER-2 belongs to the human epidermal growth factor receptor (HER) family. Via different signal transduction pathways, HER-2 regulates normal cell proliferation, survival, and differentiation. Recently, it was reported that MCF10A, BT474, and MDA-MB-231 cells bearing the HER2 K753E mutation were resistant to lapatinib. Present study revealed that HER-2 mutant K753E showed some contrasting behaviour as compared to wild, L768S and V773L HER-2 in complex with lapatinib while similar to previously known lapatinib resistant L755S HER-2 mutant. Lapatinib showed stable but reverse orientation in binding site of K753E and the highest binding energy among studied HER2-lapatinib complexes but slightly lesser than L755S mutant. Results indicate that K753E has similar profile as L755S mutant for lapatinib. The interacting residues were also found different from other three studied forms as revealed by free energy decomposition and ligplot analysis.

Anticancer activity of the supercritical extract of Brazilian green propolis and its active component, artepillin C: Bioinformatics and experimental analyses of its mechanisms of action

Propolis, a resinous substance collected by honeybees by mixing their saliva with plant sources, including tree bark and leaves and then mixed with secreted beeswax, possesses a variety of bioactivities. Whereas caffeic acid phenethyl ester (CAPE) has been recognized as a major bioactive ingredient in New Zealand propolis, Brazilian green propolis, on the other hand, possesses artepillin C (ARC). In this study, we report that, similar to CAPE, ARC docks into and abrogates mortalin-p53 complexes, causing the activation of p53 and the growth arrest of cancer cells. Cell viability assays using ARC and green propolis-supercritical extract (GPSE) revealed higher cytotoxicity in the latter, supported by nuclear translocation and the activation of p53. Furthermore, in vivo tumor suppression assays using nude mice, we found that GPSE and its conjugate with γ cyclodextrin (γCD) possessed more potent anticancer activity than purified ARC. GPSE‑γCD may thus be recommended as a natural, effective and economic anticancer amalgam.

Alanine mutation of the catalytic sites of Pantothenate Synthetase causes distinct conformational changes in the ATP binding region

The enzyme Pantothenate synthetase (PS) represents a potential drug target in Mycobacterium tuberculosis. Its X-ray crystallographic structure has demonstrated the significance and importance of conserved active site residues including His44, His47, Asn69, Gln72, Lys160 and Gln164 in substrate binding and formation of pantoyl adenylate intermediate. In the current study, molecular mechanism of decreased affinity of the enzyme for ATP caused by alanine mutations was investigated using molecular dynamics (MD) simulations and free energy calculations. A total of seven systems including wild-type + ATP, H44A + ATP, H47A + ATP, N69A + ATP, Q72A + ATP, K160A + ATP and Q164A + ATP were subjected to 50 ns MD simulations. Docking score, MM-GBSA and interaction profile analysis showed weak interactions between ATP (substrate) and PS (enzyme) in H47A and H160A mutants as compared to wild-type, leading to reduced protein catalytic activity. However, principal component analysis (PCA) and free energy landscape (FEL) analysis revealed that ATP was strongly bound to the catalytic core of the wild-type, limiting its movement to form a stable complex as compared to mutants. The study will give insight about ATP binding to the PS at the atomic level and will facilitate in designing of non-reactive analogue of pantoyl adenylate which will act as a specific inhibitor for PS.

Conformational Ensembles of α-Synuclein Derived Peptide with Different Osmolytes from Temperature Replica Exchange Sampling

Intrinsically disordered proteins (IDP) are a class of proteins that do not have a stable three-dimensional structure and can adopt a range of conformations playing various vital functional role. Alpha-synuclein is one such IDP which can aggregate into toxic protofibrils and has been associated largely with Parkinson's disease (PD) along with other neurodegenerative diseases. Osmolytes are small organic compounds that can alter the environment around the proteins by acting as denaturants or protectants for the proteins. In the present study, we have conducted a series of replica exchange molecular dynamics simulations to explore the role of osmolytes, urea which is a denaturant and TMAO (trimethylamine N-oxide), a protecting osmolyte, in aggregation and conformations of the synuclein peptide. We observed that both the osmolytes have significantly distinct impacts on the peptide and led to transitions of the conformations of the peptide from one state to other. Our findings highlighted that urea attenuated peptide aggregation and resulted in the formation of extended peptide structures whereas TMAO led to compact and folded forms of the peptide.

Role of pncA gene mutations W68R and W68G in pyrazinamide resistance

Mycobacterium tuberculosis (Mtb) resistance toward anti-tuberculosis drugs is a widespread problem. Pyrazinamide (PZA) is a first line antitubercular drug that kills semi-dormant bacilli when converted into its activated form, that is, pyrazinoic acid (POA) by Pyrazinamidase (PZase) enzyme coded by pncA gene. In this study, we conducted several analyses on native and mutant structures (W68R, W68G) of PZase before and after docking with the PZA drug to explore the molecular mechanism behind PZA resistance caused due to pncA mutations. Structural changes caused by mutations were studied with respect to their effects on functionality of protein. Docking was performed to analyze the protein-drug binding and comparative analysis was done to observe how the mutations affect drug binding affinity and binding site on protein. Native PZase protein was observed to have the maximum binding affinity in terms of docking score as well as shape complementarity in comparison to the mutant forms. Molecular dynamics simulation analyses showed that mutation in the 68th residue of protein results in a structural change at its active site which further affects the biological function of protein, that is, conversion of PZA to POA. Mutations in the protein thereby led to PZA resistance in the bacterium due to the inefficient binding.

Machine Learning and Molecular Dynamics Based Insights into Mode of Actions of Insulin Degrading Enzyme Modulators

BACKGROUND

Alzheimer's disease (AD) is one of the most common lethal neurodegenerative disorders having impact on the lives of millions of people worldwide. The disease lacks effective treatment options and the unavailability of the drugs to cure the disease necessitates the development of effectual anti-Alzheimer drugs. Several mechanisms have been reported underlying the association of the two disorders, diabetes and dementia, one among which is the insulin-degrading enzyme (IDE) which is known to degrade insulin as well beta-amyloid peptides.

METHODS

The present study is aimed to generate accurate classification models using machine learning techniques, which could identify IDE modulators from a bioassay dataset consisting of IDE inhibitors as well as non-inhibitors. The identified compounds were subjected to docking and Molecular dynamics (MD) studies for an in-depth analysis of the binding modes along with the complex stability. This study proposes that the identified potential active compounds, STK026154 (PubChem ID: CID2927418) with Glide score of -7.70 kcal/mol and BAS05901102 (PubChem ID: CID3152845) with Glide score of -7.06 kcal/mol, could serve as promising leads for the development of novel drugs against AD.

CONCLUSION

The present study shows that such in silico approaches can be effectively used to discover and select active compounds from unseen data for accelerated drug development process. The machine learning models generated in the present study were used to screen Traditional Chinese Medicine (TCM) database to identify the phytocompounds already been reported to have therapeutic effects against AD.

In silico analysis of natural compounds targeting structural and nonstructural proteins of chikungunya virus

Background: Chikungunya fever presents as a high-grade fever during its acute febrile phase and can be prolonged for months as chronic arthritis in affected individuals. Currently, there are no effective drugs or vaccines against this virus. The present study was undertaken to evaluate protein-ligand interactions of all chikungunya virus (CHIKV) proteins with natural compounds from a MolBase library in order to identify potential inhibitors of CHIKV. Methods: Virtual screening of the natural compound library against four non-structural and five structural proteins of CHIKV was performed. Homology models of the viral proteins with unknown structures were created and energy minimized by molecular dynamic simulations. Molecular docking was performed to identify the potential inhibitors for CHIKV. The absorption, distribution, metabolism and excretion (ADME) toxicity parameters for the potential inhibitors were predicted for further prioritization of the compounds. Results: Our analysis predicted three compounds, Catechin-5-O-gallate, Rosmarinic acid and Arjungenin, to interact with CHIKV proteins; two (Catechin-5-O-gallate and Rosmarinic acid) with capsid protein, and one (Arjungenin) with the E3. Conclusion: The compounds identified show promise as potential antivirals, but further in vitro studies are required to test their efficacy against CHIKV.

Cheminformatics Based Machine Learning Approaches for Assessing Glycolytic Pathway Antagonists of Mycobacterium tuberculosis

BACKGROUND

Tuberculosis is the second leading cause of death from an infectious disease worldwide after HIV, thus reasoning the expeditions in antituberculosis research. The rising number of cases of infection by resistant forms of M. tuberculosis has given impetus to the development of novel drugs that have different targets and mechanisms of action against the bacterium.

METHODS

In this study, we have used machine learning algorithms on the available high throughput screening data of inhibitors of fructose bisphosphate aldolase, an enzyme central to the glycolysis pathway in M. tuberculosis, to build predictive classification models to identify actives against Mycobacterium tuberculosis, the causative organism of tuberculosis. We used Naïve Bayes, Random Forest and C4.5 J48 algorithms available from Weka were used for building predictive classification models. Additionally, a set of most relevant attributes was selected using genetic search algorithm which offered improved model performance by avoiding over fitting and generating faster and cost effective models.

RESULTS

The model built using machine learning methods in this study provided good accuracy of classification of test compounds which suggests that in silico methods can be successfully used for screening of large datasets to identify potential drug leads. The substructure fragment analysis serves to further potentiate the M. tuberculosis drug development process as it would facilitate identification of structural fragments that are responsible for biological activity against this crucial glycolysis pathway target.

Simulation Based Investigation of Deleterious nsSNPs in ATXN2 Gene and Its Structural Consequence Toward Spinocerebellar Ataxia

Spinocerebellar degeneration, termed as ataxia is a neurological disorder of central nervous system, characterized by limb in-coordination and a progressive gait. The patient also demonstrates specific symptoms of muscle weakness, slurring of speech, and decreased vibration senses. Expansion of polyglutamine trinucleotide (CAG) within ATXN2 gene with 35 or more repeats, results in spinocerebellar ataxia type-2. Protein ataxin-2 coded by ATXN2 gene has been reported to have a crucial role in translation of the genetic information through sequestering the histone acetyl transferases (HAT) resulting in a state of hypo-acetylation. In the present study, we have evaluated the outcome for 122 non synonymous single nucleotide polymorphisms (nsSNPs) reported within ATXN2 gene through computational tools such as SIFT, PolyPhen 2.0, PANTHER, I-mutant 2.0, Phd-SNP, Pmut, MutPred. The apo and mutant (L305V and Q339L) form of structures for the ataxin-2 protein were modeled for gaining insights toward 3D spatial arrangement. Further, molecular dynamics simulations and structural analysis were performed to observe the brunt of disease associated nsSNPs toward the strength and secondary properties of ataxin-2 protein structure. Our results showed that, L305V is a highly deleterious and disease causing point substitution. Analysis based on RMSD, RMSF, Rg, SASA, number of hydrogen bonds (NH bonds), covariance matrix trace, projection analysis for eigen vector demonstrated a significant instability and conformation along with rise in mutant flexibility values in comparison to the apo form of ataxin-2 protein. The study provides a blue print of computational methodologies to examine the ataxin-blend SNPs. J. Cell. Biochem. 119: 499-510, 2018. © 2017 Wiley Periodicals, Inc.

Molecular Modeling and Virtual Screening Approach to Discover Potential Antileishmanial Inhibitors Against Ornithine Decarboxylase

BACKGROUND

Visceral leishmaniasis (VL) is a tropical neglected disease, which encounters poorest of poor people living in Asia, Africa and Latin America; causing the mortality of more than 30,000 people worldwide. The armamentarium for the treatment of VL cases is limited and continuously facing decreasing of efficacy for existing drugs. Ornithine decarboxylase (ODC) is one of the interesting drug targets in Leishmania donovani, due to its association with redox metabolism.

OBJECTIVE

To search an antileishmanial compound showing the inhibitory effect against ornithine decarboxylase of Leishmania donovani Method: In this study, we have modelled the three dimensional structure of ODC using Phyre2 (Protein Homology/analog Y Recognition Engine V 2.0), followed by validation using VADAR (Volume, Area, Dihedral Angle Reporter), RAMPAGE, ERRAT, Verify3D and ProSA (Protein Structure Analysis). In order to develop potential antileishmanial, we conducted a high throughput virtual screening of ZINC database ligands comprising of 135,966 compounds. Furthermore, QikProp, ADMET predictor and MM-GBSA was performed for ADME (Absorption, Distribution, Metabolism and Elimination), toxicity and binding energy prediction for top ligands, respectively. Finally, molecular dynamics simulation was performed to get potential antileishmanial compounds.

RESULT

Screening of zinc database compounds using high throughput virtual screening has given twelve compounds with good inhibition activity against ornithine decarboxylase. Furthermore, the molecular dynamics simulation work reveals that ZINC67909154 could be a potent inhibitor and this compound can be used to combat VL disease Conclusion: This study concludes that ZINC67909154 has the great potential to inhibit L. donovani ODC and would add to the drug discovery process against visceral leishmaniasis.

Double Mutants in DNA Gyrase Lead to Ofloxacin Resistance in Mycobacterium tuberculosis

Fluoroquinolones are among the most important classes of highly effective antibacterial drugs, exhibiting wide range of activity to cure infectious diseases. Ofloxacin is second generation fluoroquinolone approved by FDA for the treatment of tuberculosis by selectively inhibiting DNA gyrase. However, the emergence of drug resistance owing to mutations in DNA gyrase poses intimidating challenge for the effective therapy of this drug. The double mutants GyrA^A90V GyrB^D500N and GyrA^A90V GyrB^T539N are reported to be implicated in conferring higher levels of OFX resistance. The present study was designed to unravel the molecular principles behind development of resistance by the bug against fluoroquinolones. Our results highlighted that polar interactions play critical role in the development of drug resistance and highlight the significant correlation between the free energy calculations predicted by MM-PBSA and stability of the ligand-bound complexes. Modifications at the OFX binding pocket due to amino acid substitution leads to fewer hydrogen bonds in mutants DNA gyrase-OFX complex, which determined the low susceptibility of the ligand in inhibiting the mutant protein. This study provides a structural rationale to the mutation-based resistance to ofloxacin and will pave way for development potent fluoroquinolone-based resistant-defiant drugs. J. Cell. Biochem. 118: 2950-2957, 2017. © 2017 Wiley Periodicals, Inc.