Biology subjects

Saxena, A. K.

Publications and source records attributed to Saxena, A. K..

10 recordsLinked to original sources

bioRxiv2026

Structural and biochemical analysis of the Estrogen-Related Receptor alpha and complex with TMPRSS2 promoter DNA

In TMPRSS2 fusion-positive prostate cancer, ERR is involved in regulation of ERG and promotes the androgen receptor independent signaling in the cancer progression. The ERR binds to the ERREs (estrogen-related receptor response elements) present at -5042 bp of the TMPRSS2- promoter and enhances the ERG overexpression that causes prostate cancer progression. To dissect the structural basis of the ERR recognition to the TMPRSS2 promoter DNA, we have purified the full-length ERR (ERRFL), NTD deleted construct (ERR{Delta}NTD), and the DNA-binding domain (ERRDBD) proteins and performed the binding analysis with 30 bp TMPRSS2-promoter DNA (5' -AGTCCAAGGTCGGTGGATC ACAAGGTCAGG-3'). Circular dichroism analysis showed that all three ERR proteins adopt native secondary structures. DNA binding induced subtle changes in the secondary structures, while enhancing the thermal stability (Tm) of all ERRa proteins. Binding analysis showed that ERRDBD bound weakly to the DNA, whereas ERRFL and ERR{Delta}NTD exhibited substantially higher affinities ~120-fold and ~131-fold than ERRaDBD, respectively. Small-angle X-ray scattering (SAXS) analyses revealed a dimeric ERRFL structure and an ERRFL-DNA complex (2:1) structure in solution and fitted well with Alpha Fold model of apo and DNA bound complex of ERRFL. Furthermore, 100 ns dynamics simulations on apo and DNA-bound ERRa proteins showed that all proteins remained structurally stable, with flexibility largely confined to loop regions of ERRa proteins. Our biophysical, DNA binding and structural analyses have revealed the mechanism involved in ERR recognition of the TMPRSS2- promoter DNA, which provides insight into ERR-mediated transcriptional regulation and development of anticancer drugs against ERR-driven prostate cancer.

cancer biology↗

bioRxiv2021

Dissection of function and recognition mechanism of M. tuberculosis ESX-1 secreted virulence factor EspC

Mycobacterium tuberculosis uses the ESAT-6 system-1/type VII (ESX-1) system for secretion of virulence proteins into the host cell, however the mechanism of virulence proteins secretion, molecular components and regulation of ESX-1 system are only partly understood. In the current study, we have analyzed the biological function and recognition mechanism between ESX-1 virulence EspC and EccA1 ATPase proteins. The EspC enters into A549 human lung carcinoma cells and exhibited cytotoxicity, as observed in MTT Assay. To understand the recognition mechanism between EspC and EccA1 ATPase, the EspC and EccA1 mutants were generated based on EspC~EccA1 interactions, as observed in molecular modeling. Binding analysis shows that EspC export arm interacts specifically to the {beta}-hairpin insertion motif of the TPR domain of EccA1 ATPase. Mutations in these epitopes lead to significant decrease/or abolish the binding between EspC and EccA1 ATPase. Our study provides insight into biological function and recognition mechanism between EspC and EccA1 ATPase, which can be used as target to prevent EspC secretion/ or in general virulence factor secretion by mycobacterial ESX-1 system.

biophysics↗

bioRxiv2021

Exploring the structural basis to develop efficient multi-epitope vaccines displaying interaction with HLA and TAP and TLR3 molecules to prevent NIPAH infection, a global threat to human health

BackgroundNipah virus (NiV) is an emerging zoonotic virus that caused several serious outbreaks in the South Asian region with high mortality rates ranging from 40 to 90% since 2001. NiV infection causes lethal encephalitis and respiratory disease with the symptom of endothelial cell-cell fusion. No specific vaccine has yet been reported against NiV. Methodology and Principal FindingsRecently, the design of some Multi-Epitope Vaccines (MEV) has been proposed but that involves vary limited number of epitopes which limits the potential of vaccine. To address the urgent need for a specific and effective vaccine against NiV infection, in the present study, we have designed two MEVs composed of 33 Cytotoxic T lymphocyte (CTL) epitopes and 38 Helper T lymphocyte (HTL) epitopes. Both the MEVs carry potential B cell linear epitope overlapping regions, B cell discontinuous epitopes as well as IFN-{gamma} inducing epitopes. Hence the designed MEVs carry potential to elicit cell-mediated as well as humoral immune response. Selected CTL and HTL epitopes were validated for their stable molecular interactions with HLA class I and II alleles as well as in case of CTL epitopes, with human transporter associated with antigen processing (TAP). Human {beta}-defensin 2 and {beta}-defensin 3 were used as adjuvants to enhance the immune response of both the MEVs. Molecular dynamics simulation studies of MEVs-TLR3 ectodomain (Toll-Like Receptor 3) complex indicate the stable molecular interaction. Further, the codon optimized cDNA of both the MEVs has shown high expression potential in the mammalian host cell line (Human). Hence for further studies, the designed MEV constructs could be expressed and tried in-vivo as potential vaccine candidates against NiV. ConclusionWe conclude that the MEVs designed and in silico validated here could be highly potential vaccine candidate to combat NiV, with greater effectiveness, high specificity and large human population coverage worldwide. AUTHOR SUMMARYNipah Virus (NiV) has caused several outbreaks in past two decades calming large number of human lives. Our present work aims to design and in silico validate Multi-Epitope Vaccine against NiV. The current approach to design vaccine involves whole virus or full length proteins as vaccine candidates against NiV. These approaches carry chances of raising the unwanted non-neutralizing antibodies which have been found to cause clinical complexities. Recently few Multi-Epitope vaccines have also been proposed, but they have involved limited number of epitopes for vaccine design in result limiting the effectiveness and human population coverage. Here in our MEVs we have involved all the proteins of NiV to design the vaccine. Moreover since we have used in silico validated epitopes we may conclude that the here proposed MEVs would be highly specific, effective and potential vaccine candidate to combat NiV with large human population coverage worldwide.

immunology↗

bioRxiv2021

Structural and biochemical analysis of ATPase activity and EsxAB substrate binding of M. tuberculosis EccCb1 enzyme

The EccC enzyme of M. tuberculosis ESX-1 system is a promising target for antivirulence drug development. The EccC enzyme comprises two polypeptides (i) EccCa1, a membrane bound enzyme having two ATPase domains D2 & D3 (ii) cytosolic EccCb, which contains two ATPase domains. In current study, we have analyzed the low-resolution structure of EccCb1, performed ATPase activity and EsxAB substrate binding analysis. The EccCb1 enzyme eluted as oligomer from size exclusion column and small angle X-ray scattering analysis revealed the double hexameric structure in solution. The EccCb1 enzyme showed catalytic efficiency (kcat/KM)[~] 0.020{+/-}0.005 M-1 min-1, however [~] 3.7 fold lower than its D2 and [~]1.7 fold lower than D3 domains respectively. The D2 and D3 domains exhibited the ATPase activity and mutation of residues involved in ATP+Mg2+ binding have yielded 56-94% reduction in catalytic efficiency for both D2 and D3 domains. The EccCb1 binds the EsxAB substrate with KD [~] 11.4{+/-}3.4 nM via specific groove located at C-terminal region of D3 domain. ATP binding to EccCb1 enhanced the EsxAB substrate binding by [~] 3 fold, indicating ATPase energy involvement in EsxAB substrate translocation. We modeled the dodecameric EccCb1+EsxAB+ ATP+Mg2+ complex, which showed the binding pockets involved in ATP+Mg2+ and EsxAB substrate binding. The enzyme dynamics involved in ATP+Mg2+ and EsxAB substrate recognition were identified and showed the enhanced stability of EccCb1 enzyme as a result of ligand binding. Overall, our structural and biochemical analysis showed the low-resolution structure and mechanism involved in ATPase activity and EsxAB substrate binding and dynamics involved in EsxAB substrate and ATP+Mg2+ recognition. Overall, our structural and biochemical data on EccCb1 will contribute significantly in development of antivirulence inhibitors, which will prevent virulence factor secretion by M. tuberculosis ESX-1 system.

biophysics↗

bioRxiv2020

Structural studies on M. tuberculosis decaprenyl phosphoryl-β-D-ribose epimerase-2 enzyme involved in cell wall biogenesis

The Mycobacterium DprE2 is a NADH-dependent enzyme and converts the decaprenylphosphoryl-{beta}-D-ribose (DPX) to decaprenylphosphoryl-{beta}-D-arabinofuranose (DPA). The FAD-containing oxidoreductase MtbDprE1 and NADH-dependent reductase MtbDprE2 enzymes catalyses together the epimerization reaction, which coverts DPR to DPA. Here, MtbDprE2 enzyme was purified and structurally characterized using circular dichroism, molecular modelling and dynamics simulation techniques. The MtbDprE2 was purified, which eluted as oligomer from size exclusion column. The circular dichroism analysis yielded ~ 47.6% -helix, ~ 19.8% {beta}-sheet and ~ 32.6% random coil structures in MtbDprE2 enzyme and showed highly thermostability. The molecular modelling of MtbDprE2 and its complex with NADH showed that it contains two domains (i) the large domain consists of central twisted seven {beta}-sheets decorated by eight -helices and (ii) a small domain contains two short -helices connect by loop. Overall, the MtbDprE2 adopts a typical short-chain dehydrogenase rossmann fold and NADH binds to Asp69, Ser147, Tyr160, Lys164 of catalytic triad and Gly16, Ser19, Glu20, Ile21 of Gly-rich motif of MtbDprE2. 1 ns dynamics simulation was performed on apo and NADH bound MtbDprE2, which indicated the small conformational change in ligand binding site, which resulted more closed pocket than open pocket observed in apo enzyme. Small conformational changes were observed in active site residues and orientation between large and small domains of MtbDprE2 upon NADH binding. Current knowledge of MtbDprE2 structure and its NADH binding mechanism will contribute significantly in development of specific inhibitors against M. tuberculosis.

bioinformatics↗

bioRxiv2020

Computationally validated SARS-CoV-2 CTL and HTL Multi-Patch Vaccines designed by reverse epitomics approach, shows potential to cover large ethnically distributed human population worldwide

BackgroundThe SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) is a positive-sense single-stranded RNA coronavirus responsible for the ongoing 2019-2020 COVID-19 outbreak. The highly contagious COVID-19 disease has spread to 216 countries in less than six months. Though several vaccine candidates are being claimed, an effective vaccine is yet to come. In present study we have designed and theoretically validated novel Multi-Patch Vaccines against SARS-CoV-2. MethodologyA novel reverse epitomics approach, "overlapping-epitope-clusters-to-patches" method is utilized to identify multiple antigenic regions from the SARS-CoV-2 proteome. These antigenic regions are here termed as "Ag-Patch or Ag-Patches", for Antigenic Patch or Patches. The identification of Ag-Patches is based on clusters of overlapping epitopes rising from a particular region of SARS-CoV-2 protein. Further, we have utilized the identified Ag-Patches to design Multi-Patch Vaccines (MPVs), proposing a novel methodology for vaccine design and development. The designed MPVs were analyzed for immunologically crucial parameters, physiochemical properties and cDNA constructs. ResultsWe identified 73 CTL (Cytotoxic T-Lymphocyte), 49 HTL (Helper T-Lymphocyte) novel Ag-Patches from the proteome of SARS-CoV-2. The identified Ag-Patches utilized to design MPVs cover 768 (518 CTL and 250 HTL) overlapping epitopes targeting different HLA alleles. Such large number of epitope coverage is not possible for multi-epitope vaccines. The large number of epitopes covered implies large number of HLA alleles targeted, and hence large ethnically distributed human population coverage. The MPVs:Toll-Like Receptor ectodomain complex shows stable nature with numerous hydrogen bond formation and acceptable root mean square deviation and fluctuation. Further, the cDNA analysis favors high expression of the MPVs constructs in human cell line. ConclusionHighly immunogenic novel Ag-Patches are identified from the entire proteome of SARS CoV-2 by a novel reverse epitomics approach. We conclude that the novel Multi-Patch Vaccines could be a highly potential novel approach to combat SARS-CoV-2, with greater effectiveness, high specificity and large human population coverage worldwide. O_FIG O_LINKSMALLFIG WIDTH=187 HEIGHT=200 SRC="FIGDIR/small/284992v1_ufig1.gif" ALT="Figure 1"> View larger version (84K): org.highwire.dtl.DTLVardef@176f27org.highwire.dtl.DTLVardef@82a4fcorg.highwire.dtl.DTLVardef@11db43forg.highwire.dtl.DTLVardef@12495b2_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOABSTRACT FIGURE:C_FLOATNO A Multi-Patch Vaccine design to combat SARS-CoV-2 and a method to prepare thereof. Multi-Patch Vaccine designing to combat SARS-CoV-2 infection by reverse epitomics approach, "Overlapping-epitope-clusters-to-patches" method. C_FIG

immunology↗

bioRxiv2020

Structural basis to design multi-epitope vaccines against Novel Coronavirus 19 (COVID19) infection, the ongoing pandemic emergency: an in silico approach

The 2019 novel coronavirus (COVID19 / Wuhan coronavirus), officially named as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), is a positive-sense single-stranded RNA coronavirus. SARS-CoV-2 causes the contagious COVID19 disease also known as 2019-nCoV acute respiratory disease and has led to the ongoing 2019-20 pandemic COVID19 outbreak. The effective counter measures against SARS-CoV-2 infection require the design and development of specific and effective vaccine candidate. In the present study, we have screened and shortlisted 38 CTL, 33 HTL and 12 B cell epitopes from the eleven Protein sequences of SARS-CoV-2 by utilizing different in silico tools. The screened epitopes were further validated for their binding with their respective HLA allele binders and TAP (Transporter associated with antigen processing) molecule by molecular docking. The shortlisted screened epitopes were further utilized to design novel two multi-epitope vaccines (MEVs) composed of CTL, HTL and B cell epitopes overlaps with potential to elicit humoral as well as cellular immune response against SARS-CoV-2. To enhance the immune response for our vaccine design, truncated (residues 10-153) Onchocerca volvulus activation-associated secreted protein-1 (Ov-ASP-1) has been utilized as an adjuvant at N terminal of both the MEVs. Further molecular models for both the MEVs were prepared and validated for their stable molecular interactions with Toll-Like Receptor 3 (TLR 3). The codon-optimized cDNA of both the MEVs were further analyzed for their potential of high level of expression in a human cell line. The present study is very significant in terms of molecular designing of prospective CTL and HTL vaccine against SARS-CoV-2 infection with the potential to elicit cellular as well as humoral immune response. (SARS-CoV-2), Coronavirus, Human Transporter associated with antigen processing (TAP), Toll-Like Receptor (TLR), Epitope, Immunoinformatics, Molecular Docking, Molecular dynamics simulation, Multi-epitope Vaccine Graphical abstractThe designed CTL (Cytotoxic T lymphocyte) and HTL (Helper T lymphocyte) multi-epitope vaccines (MEV) against COVID19 infection. Both the CTL and HTL MEV models show a very stable and well fit conformational complex formation tendency with the Toll like receptor 3. CTL and HTL MEVs: ribbon; Toll like receptor 3: gray cartoon; Adjuvant [truncated (residues 10-153) Onchocerca volvulus activation-associated secreted protein-1]: orange ribbon regions; Epitopes: cyan ribbons regions; 6xHis Tag: magenta ribbon regions. O_FIG O_LINKSMALLFIG WIDTH=87 HEIGHT=200 SRC="FIGDIR/small/019299v2_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@6cb749org.highwire.dtl.DTLVardef@1752d54org.highwire.dtl.DTLVardef@1f2fc16org.highwire.dtl.DTLVardef@18415a9_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

bioRxiv2019

The impact of distillery effluent irrigation on plant-growth-promoting traits and taxonomic composition of bacterial communities in agricultural soil

Long-term irrigation of agricultural fields with distillery effluent (DE) may alter the physical, chemical and biological properties of the soil. Microorganisms are critical to the maintenance of soil health and productivity. However, the impact of DE irrigation on activity and taxonomy of soil microorganisms is poorly understood. Here we studied plant-growth-promoting (PGP) traits and taxonomic composition of bacterial communities in agricultural soil irrigated with DE in conjugation with irrigation water, using cultivation-dependent and - independent methods. Most of the bacterial isolates obtained from DE irrigated soil were found to display PGP traits (phosphate solubilization, siderophore, indolic compounds and ammonia production). Diverse bacterial taxa were found in both culturable bacterial community and 16S rRNA gene clone library, which belonged to bacterial phyla Proteobacteria (Alpha-, Beta- and Gamma- subdivisions), Firmicutes, Actinobacteria, Acidobacteria, Bacteroidetes and Gemmatimonadates. Overall, these results indicate that PGP traits and taxonomic diversity of soil bacterial communities were not severely impacted by DE irrigation.

microbiology↗

bioRxiv2018

Synthesis, SAR and Docking Studies of Substituted Aryl phenylthiazolyl phenylcarboxamide as potential Protein Tyrosine Phosphatase 1B Inhibitors

Inspired by the potent PTP1B inhibitory activity reported in a novel series of substituted aryl thiazolyl phenylsulphonamides (I), sulfonyl moiety in the most active compound (I, R= OCH3, R1= CF3, 73.6% PTP1B inhibition) was replaced by benzoyl group (region B) to afford compound II which showed lesser activity (50.5% PTP1B inhibition). To optimize the activity, further structural modifications were done on compound II at region A, B and C to design and synthesize a series of 24 aryl phenylthiazolyl phenylcarboxamides for evaluation against PTP1B enzyme. Among these compounds six compounds showed good PTP1B inhibitory activity in the order of compound 38 > 30 > 29 > 37 > 22 > 19. The lowest energy conformer of compound 38 at PTP1B active site shows favorable binding similar to known PTP1B binders and explains its selectivity towards PTP1B. Compound 38 also showed promising antihyperglycemic, antidyslipidemic and insulin resistant reversal activities in vivo in STZ model and db/db mice model. Altogether, the compound 38 present an excellent candidate for future PTP1B targeted drug discovery.

pharmacology and toxicology↗

bioRxiv2018

Triple layered QSAR Studies on Substituted 1,2,4-Trioxanes as potential antimalarial agents: Superiority of the Quantitative Pharmacophore-Based Alignment, Over Common Substructure based Alignment

The present study reports the utilization of three approaches viz Pharmacophore, CoMFA, CoMSIA and HQSAR studies to identify the essential structural requirements in 3D chemical space for the modulation of the antimalarial activity of substituted 1,2,4 trioxanes. The superiority of Quantitative pharmacophore based alignment (QuantitativePBA) over global minima energy conformer-based alignment (GMCBA) has been reported in CoMFA and CoMSIA studies. The developed models showed good statistical significance in internal validation (q2, group cross-validation and bootstrapping) and performed very well in predicting antimalarial activity of test set compounds. Structural features in terms of their steric, electrostatic, and hydrophobic interactions in 3D space have been found important for the antimalarial activity of substituted 1,2,4-trioxanes. Further, the HQSAR studies based on the same training and test set acted as an additional tool to find the sub-structural fingerprints of substituted 1,2,4 trioxanes for their antimalarial activity. Together, these studies may facilitate the design and discovery of new substituted 1,2,4-trioxane with potent antimalarial activity.

bioinformatics↗