Unveiling the intricacies of allosteric regulation in aspartate kinase from the Wolbachia endosymbiont of Brugia Malayi: Mechanistic and therapeutic insights.

Aspartate kinase (AK), an enzyme from the Wolbachia endosymbiont of Brugia malayi (WBm), plays a pivotal role in the bacterial cell wall and amino acid biosynthesis, rendering it an attractive candidate for therapeutic intervention. Allosteric inhibition of aspartate kinase is a prevalent mode of regulation across microorganisms and plants, often modulated by end products such as lysine, threonine, methionine, or meso-diaminopimelate. The intricate and diverse nature of microbial allosteric regulation underscores the need for rigorous investigation. This study employs a combined experimental and computational approach to decipher the allosteric regulation of WBmAK. Molecular Dynamics (MD) simulations elucidate that ATP (cofactor) and ASP (substrate) binding induce a closed conformation, promoting enzymatic activity. In contrast, the binding of lysine (allosteric inhibitor) leads to enzyme inactivation and an open conformation. The enzymatic assay demonstrates the optimal activity of WBmAK at 28 °C and a pH of 8.0. Notably, the allosteric inhibition study highlights lysine as a more potent inhibitor compared to threonine. Importantly, this investigation sheds light on the allosteric mechanism governing WBmAK and imparts novel insights into structure-based drug discovery, paving the way for the development of effective inhibitors against filarial pathogens.

Structural and functional characterization of 6-phosphogluconate dehydrogenase in Plasmodium falciparum (3D7) and identification of its potent inhibitors.

The malarial parasite Plasmodium falciparum predominantly causes severe malaria and deaths worldwide. Moreover, resistance developed by P. falciparum to frontline drugs in recent years has markedly increased malaria-related deaths in South Asian Countries. Ribulose 5-phosphate and NADPH synthesized by Pentose Phosphate Pathway (PPP) act as a direct precursor for nucleotide synthesis and P. falciparum survival during oxidative challenges in the intra-erythrocytic growth phase . In the present study, we have elucidated the structure and functional characteristics of 6-phosphogluconate dehydrogenase (6PGD) in P. falciparum and have identified potent hits against 6PGD by pharmacophore-based virtual screening with ZINC and ChemBridge databases. Molecular docking and Molecular dynamics simulation, binding free energies (MMGBSA & MMPBSA), and Density Functional Theory (DFT) calculations were integratively employed to validate and prioritize the most potential hits. The 6PGD structure was found to have an open and closed conformation during MD simulation. The apo form of 6PGD was found to be in closed conformation, while a open conformation attributed to facilitating binding of cofactor. It was also inferred from the conformational analysis that the small domain of 6PGD has a high influence in altering the conformation that may aid in open/closed conformation of 6PGD. The top three hits identified using pharmacophore hypotheses were ChemBridge_11084819, ChemBridge_80178394, and ChemBridge_17912340. Though all three hits scored a high glide score, MMGBSA, and favorable ADMET properties, ChemBridge_11084819 and ChemBrdige_17912340 showed higher stability and binding free energy. Moreover, these hits also featured stable H-bond interactions with the active loop of 6PGD with binding free energy comparable to substrate-bound complex. Therefore, the ChemBridge_11084819 and ChemBridge_17912340 moieties demonstrate to have high therapeutic potential against 6PGD in P. falciparum.Communicated by Ramaswamy H. Sarma.

Exploring the antimicrobial potential of 4,5,7-trihydroxyflavanone (THF) against vancomycin-resistant Enterococcus gallinarum infections: in vitro and in silico investigations.

Enterococcus gallinarum and other Enterococcus species commonly inhabit the human gastrointestinal tract. While the pathogenicity of Enterococcus gallinarum remains incompletely understood, its infections are alarmingly severein humans, as evidenced by numerous cases. Formerly, Vancomycin was the preferred drug, but recent findings indicate that clinical isolates of Enterococcus gallinarum are resistant, leading to the emergence of vancomycin-resistant enterococci (VRE) strains. The escalation of drug resistance is often linked to overexpressed virulence factors, some of which are implicated in biofilm formation in Enterococcus infections. Henceforth, this research investigates the potential of phytocompounds to combat E. gallinarum infection, employing both in vitro and in silico methodologies. In vitro techniques were employed to assess the efficacy of various phytocompounds, ultimately identifying 4,5,7-trihydroxyflavanone (THF) as particularly effective in inhibiting microbial growth. THF displayed over 80% antibacterial activity at 200 µg/ml against E. gallinarum. Subsequent qualitative and quantitative hemolysin assays implicated hemolysin as a target of THF. Molecular docking analysis of THF and Hemolysin A revealed a strong binding affinity. Notably, residues Asn18, Asp85, and His199 formed hydrogen bonds, while His22 and His86 were involved in robust π-π stacking and π-cation interactions with THF. Overall, this study highlights THF's potential in combating E. gallinarum infections.Communicated by Ramaswamy H. Sarma.

Harnessing allosteric inhibition: prioritizing LIMK2 inhibitors for targeted cancer therapy through pharmacophore-based virtual screening and essential molecular dynamics.

The therapeutic potential of small molecule kinase inhibitors in cancer treatment is well recognized. However, achieving selectivity remains a formidable challenge, primarily due to the structural similarity of ATP binding pockets among kinases. Allosteric inhibition, which involves targeting binding pockets beyond the ATP-binding site, provides a promising alternative to overcome this challenge. In this study, a meticulous approach was implemented to prioritize type 3 inhibitors for LIMK2, employing a range of techniques including Molecular Dynamics (MD) simulations, e-pharmacophore-guided High Throughput Virtual Screening (HTVS), MM/GBSA and ADMETox analyses, Density Functional Theory (DFT) calculations, and MM/PBSA investigations. The e-pharmacophore model identifies a hypothesis featuring five essential pharmacophoric elements (RRRAH). Through virtual screening of the ZINC compound database, we identified only five compounds that align with all four pharmacophoric features: ZINC1044382792, ZINC1433610865, ZINC1044109145, ZINC952869440, and ZINC490621334. These compounds not only exhibit higher binding affinity but also demonstrate favorable ADME/Tox profiles. Molecular dynamics simulations underscore the stability of hydrogen bond interactions with critical cryptic LIMK2 pocket residues, Asp469 and Arg474, only for two compounds: ZINC143361086 and ZINC1044382792. These compounds also exhibit superior occupancy interactions, as indicated by HOMO-LUMO analysis. Additionally, binding free energy calculations highlight the significant affinities of these two compounds when complexed with LIMK2: -83.491 ± 1.230 kJ/mol and -90.122 ± 1.248 kJ/mol for ZINC1044382792 and ZINC1433610862, respectively. Hence, this comprehensive investigation identifies ZINC1433610862 and ZINC1044382792 as prospective hits, representing promising leads for targeting LIMK2 in cancer therapeutics.Communicated by Ramaswamy H. Sarma.

Structural snapshots of Mycobacterium tuberculosis enolase reveal dual mode of 2PG binding and its implication in enzyme catalysis.

Enolase, a ubiquitous enzyme, catalyzes the reversible conversion of 2-phosphoglycerate (2PG) to phosphoenolpyruvate (PEP) in the glycolytic pathway of organisms of all three domains of life. The underlying mechanism of the 2PG to PEP conversion has been studied in great detail in previous work, however that of the reverse reaction remains to be explored. Here we present structural snapshots of Mycobacterium tuberculosis (Mtb) enolase in apo, PEP-bound and two 2PG-bound forms as it catalyzes the conversion of PEP to 2PG. The two 2PG-bound complex structures differed in the conformation of the bound product (2PG) viz the widely reported canonical conformation and a novel binding pose, which we refer to here as the alternate conformation. Notably, we observed two major differences compared with the forward reaction: the presence of MgB is non-obligatory for the reaction and 2PG assumes an alternate conformation that is likely to facilitate its dissociation from the active site. Molecular dynamics studies and binding free energy calculations further substantiate that the alternate conformation of 2PG causes distortions in both metal ion coordination and hydrogen-bonding interactions, resulting in an increased flexibility of the active-site loops and aiding product release. Taken together, this study presents a probable mechanism involved in PEP to 2PG catalysis that is likely to be mediated by the conformational change of 2PG at the active site.

Impact of Surface Charge-Tailored Gold Nanorods for Selective Targeting of Mitochondria in Breast Cancer Cells Using Photodynamic Therapy.

Herein, the impact of surface charge tailored of gold nanorods (GNRs) on breast cancer cells (MCF-7 and MDA-MB-231) upon conjugation with triphenylphosphonium (TPP) for improved photodynamic therapy (PDT) targeting mitochondria was studied. The salient features of the study are as follows: (i) positive (CTAB@GNRs) and negative (PSS-CTAB@GNRs) surface-charged gold nanorods were developed and characterized; (ii) the mitochondrial targeting efficiency of gold nanorods was improved by conjugating TPP molecules; (iii) the conjugated nanoprobes (TPP-CTAB@GNRs and TPP-PSS-CTAB@GNRs) were evaluated for PDT in the presence of photosensitizer (PS), 5-aminolevulinic acid (5-ALA) in breast cancer cells; (iv) both nanoprobes (TPP-CTAB@GNRs and TPP-PSS-CTAB@GNRs) induce apoptosis, damage DNA, generate reactive oxygen species, and decrease mitochondrial membrane potential upon 5-ALA-based PDT; and (v) 5-ALA-PDT of two nanoprobes (TPP-CTAB@GNRs and TPP-PSS-CTAB@GNRs) impact cell signaling (PI3K/AKT) pathway by upregulating proapoptotic genes and proteins. Based on the results, we confirm that the positively charged (rapid) nanoprobes are more advantageous than their negatively (slow) charged nanoprobes. However, depending on the kind and degree of cancer, both nanoprobes can serve as efficient agents for delivering anticancer therapy.

HTNpedia: A Knowledge Base for Hypertension Research.

BACKGROUND: Hypertension is notably a serious public health concern due to its high prevalence and strong association with cardiovascular disease and renal failure. It is reported to be the fourth leading disease that leads to death worldwide. OBJECTIVE: Currently, there is no active operational knowledge base or database for hypertension or cardiovascular illness. METHOD: The primary data source was retrieved from the research outputs obtained from our laboratory team working on hypertension research. We have presented a preliminary dataset and external links to the public repository for detailed analysis to readers. RESULT: As a result, HTNpedia was created to provide information regarding hypertension-related proteins and genes. CONCLUSION: The complete webpage is accessible via www.mkarthikeyan.bioinfoau.org/HTNpedia.

Combination of bendamustine-azacitidine against Syk target of breast cancer: an in silico study.

Breast cancer (BC) is the most serious and second leading cause of death in women worldwide. When breast cancer is diagnosed and treated early, the chance of long-term survival is up to 90%. On the other hand, 90% of BC patient deaths are due to metastasis and a lack of effective early diagnosis. The existing conventional chemotherapy provides negative feedback due to transportation barriers towards the action sites, multidrug resistance, poor bio-availability, non-specific delivery and systemic side effects on the healthy tissue. Syk protein Kinase has been reported in BC, as a tumor modulator, providing a pro-survival signal and also by restricting epithelial-mesenchymal transition, enhancing cell-cell interactions and inhibiting migration. In the present study, we explored the possibility of targeting BC by attenuating Syk protein Kinase. Hence, we have conjugated the hydrophobic Bendamustine (BEN) and hydrophilic Azacitidine (AZA) anticancer drugs to evaluate their efficacy against BC. The native drugs (BEN and AZA) and designed drug-drug conjugate (BEN-AZA) were docked with Syk protein. Then, the docked complex was performed for Binding Free Energy and Molecular Dynamics Simulations. Furthermore, DFT and ADME properties were carried out. The results revealed that the designed drug-drug conjugate has a better docking score, ΔGbind and admirable stability throughout the simulation when compared with native drugs. In DFT and ADME analyses, the designed drug-drug conjugate has shown good stereo electronic features and pharmaceutical relevant parameters than that of native drugs. The overall results suggested that the designed drug-drug conjugate may be a suitable candidate for BC treatment.Communicated by Ramaswamy H. Sarma.

Triphenylphosphonium conjugated gold nanotriangles impact Pi3K/AKT pathway in breast cancer cells: a photodynamic therapy approach.

Although gold nanoparticles based photodynamic therapy (PDT) were reported to improve efficacy and specificity, the impact of surface charge in targeting cancer is still a challenge. Herein, we report gold nanotriangles (AuNTs) tuned with anionic and cationic surface charge conjugating triphenylphosphonium (TPP) targeting breast cancer cells with 5-aminoleuvinic acid (5-ALA) based PDT, in vitro. Optimized surface charge of AuNTs with and without TPP kill breast cancer cells. By combining, 5-ALA and PDT, the surface charge augmented AuNTs deliver improved cellular toxicity as revealed by MTT, fluorescent probes and flow cytometry. Further, the 5-ALA and PDT treatment in the presence of AuNTs impairs cell survival Pi3K/AKT signaling pathway causing mitochondrial dependent apoptosis. The cumulative findings demonstrate that, cationic AuNTs with TPP excel selective targeting of breast cancer cells in the presence of 5-ALA and PDT.

Designing of potent anti-diabetic molecules by targeting SIK2 using computational approaches.

Diabetes mellitus (DM) is one of the major health problems worldwide. WHO have estimated that 439 million people may have DM by the year 2030. Several classes of drugs such as sulfonylureas, meglitinides, thiazolidinediones etc. are available to manage this disease, however, there is no cure for this disease. Salt inducible kinase 2 (SIK2) is expressed several folds in adipose tissue than in normal tissues and thus SIK2 is one of the attractive targets for DM treatment. SIK2 inhibition improves glucose homeostasis. Several analogues have been reported and experimentally proven against SIK for DM treatment. But, identifying potential SIK2 inhibitors with improved efficacy and good pharmacokinetic profiles will be helpful for the effective treatment of DM. The objective of the present study is to identify selective SIK2 inhibitors with good pharmacokinetic profiles. Due to the unavailability of SIK2 structure, the modeled structure of SIK2 will be an important to understand the atomic level of SIK2 inhibitors in the binding site pocket. In this study, different molecular modeling studies such as Homology Modeling, Molecular Docking, Pharmacophore-based virtual screening, MD simulations, Density Functional Theory calculations and WaterMap analysis were performed to identify potential SIK2 inhibitors. Five molecules from different databases such as Binding_4067, TosLab_837067, NCI_349155, Life chemicals_ F2565-0113, Enamine_7623111186 molecules were identified as possible SIK2 inhibitors.

Investigation of protein-ligand binding motions through protein conformational morphing and clustering of cytochrome bc1-aa3 super complex.

Cytochrome b (QcrB) is considered an essential subunit in the electron transport chain that coordinates the action of the entire cytochrome bc1 oxidase. It has been identified as an attractive drug target for a new promising clinical candidate Q203 that depletes the intracellular ATP levels in the bacterium, Mycobacterium tuberculosis. However, single point polymorphism (T313A/I) near the quinol oxidation site of QcrB developed resistance to Q203. In the present study, we analyze the structural changes and drug-resistance mechanism of QcrB due to the point mutation in detail through conformational morphing and molecular docking studies. By morphing, we generated conformers between the open and closed state of the electron transporting cytochrome bc1-aa3 super complex. We clustered them to identify four intermediate structures and relevant intra- and intermolecular motions that may be of functional relevance, especially the binding of Q203 in wild and mutant QcrB intermediate structures and their alteration in developing drug resistance. The difference in the binding score and hydrogen bond interactions between Q203 and the wild-type and mutant intermediate structures of QcrB from molecular docking studies showed that the point mutation T313A severely affected the binding affinity of the candidate drug. Together, the findings provide an in-depth understanding of QcrB inhibition in different conformations, including closed, intermediate, and open states of cytochrome bc1-aa3 super complex in Mycobacterium tuberculosis at the atomic level. We also obtain insights for designing QcrB and cytochrome bc1-aa3 inhibitors as potential therapeutics that may combat drug resistance in tuberculosis.

Functional Characterization, Mechanism, and Mode of Action of Putative Streptomycin Adenylyltransferase from Serratia marcescens.

Nosocomial infections are serious threats to the entire world in healthcare settings. The major causative agents of nosocomial infections are bacterial pathogens, among which Enterobacteriaceae family member Serratia marcescens plays a crucial role. It is a gram-negative opportunistic pathogen, predominantly affecting patients in intensive-care units. The presence of intrinsic genes in S. marcescens led to the development of resistance to antibiotics for survival. Complete scanning of the proteome, including hypothetical and partially annotated proteins, paves the way for a better understanding of potential drug targets. The targeted protein expressed in E. coli BL21 (DE3) pLysS cells has shown complete resistance to aminoglycoside antibiotic streptomycin (>256 MCG). The recombinant protein was purified using affinity and size-exclusion chromatography and characterized using SDS-PAGE, western blotting, and MALDI-TOF analysis. Free phosphate bound to malachite green was detected at 620 nm, evident of the conversion of adenosine triphosphate to adenosine monophosphate during the adenylation process. Similarly, in the chromatographic assay, adenylated streptomycin absorbed at 260 nm in AKTA (FPLC), confirming the enzyme-catalyzed adenylation of streptomycin. Further, the adenylated product of streptomycin was confirmed through HPLC and mass spectrometry analysis. In conclusion, our characterization studies identified the partially annotated hypothetical protein as streptomycin adenylyltransferase.

Deciphering the conformational transitions of LIMK2 active and inactive states to ponder specific druggable states through microsecond scale molecular dynamics simulation.

LIMK2 inhibitors are one of the potential therapeutic modalities for treating various diseases. In the current scenario, there is a paucity of effective LIMK inhibitors that are highly specific with minimal off-target effects. To date, the conformational transitions of LIMK2 from DFGinαCin (CIDI) (active) to DFGoutαCout (CODO) (inactive) states are yet to be probed and are essential for capturing the unique, druggable conformations. Therefore, this study was intended to capture the diverse conformational states of LIMK2 for accelerating the rational identification of conformation specific inhibitors through high-end structural bioinformatics protocols. Hence, in this study, molecular modelling followed by an extensive microsecond timescale of molecular dynamics simulation was performed encompassing perturbation response scanning, metapath, and community analysis towards the conformational sampling of LIMK2. Overall this study precisely identifies the conformational ensemble of LIMK2 the intermediate inactive states namely, CIDO, CinterDinter, CIDinter, CinterDI, CinterDO, CODI, CODinter apart from CIDI and CODO. This also facilitated observing that ß8 preceding XDFG, αC (F373, L374), and αD (L413) as the major effectors that may facilitate the regulation of varying conformational transitions among the states. Additionally, the conserved ß sheets and the loops namely, C.l, b.l, and G/P.loop were observed to be involved in the metapath for allosteric communication among the intermediates with CIDI and CODO state. Moreover, only the CODO state was observed to have closed type A.l, while the CIDI and other intermediate states except for CIDO were observed to have open-DFG out type A.l, thereby enabling the binding of substrate. Apart from these, the druggable site analysis inferred that the CIDI and CODO states harbor prominent druggable sites spanning the conserved N-lobe, while the intermediates were observed to have unraveled allosteric druggable sites distal from the ATP binding site, majorly spanning the C-lobe of LIMK2. Thus, this study provides potential insights into the intermediate conformational druggable states of LIMK2 and also the druggable conformations, especially the inactive states of LIMK2, as a specific therapeutic targeting mode. Thus, providing a widened avenue to ponder the allosteric sites or the isoform selectivity conformations for targeting LIMK2 in various disease conditions.

Repurposing of Doxycycline to Hinder the Viral Replication of SARS-CoV-2: From in silico to in vitro Validation.

Since the rapid spread of coronavirus disease (COVID-19) became a global pandemic, healthcare ministries around the world have recommended specific control methods such as quarantining infected peoples, identifying infections, wearing mask, and practicing hand hygiene. Since no effective treatment for COVID-19 has yet been discovered, a variety of drugs approved by Food and Drug Administration (FDA) have been suggested for repurposing strategy. In the current study, we predicted that doxycycline could interact with the nucleotide triphosphate (NTP) entry channel, and is therefore expected to hinder the viral replication of SARS-CoV-2 RNA-dependent RNA-polymerase (RdRp) through docking analysis. Further, the molecular dynamics results revealed that the RdRp-Doxycycline complex was structurally relatively stable during the dynamic period (100 ns), and its complex maintained close contact with their active catalytic domains of SARS-CoV-2 RdRp. The molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) calculation of binding free energy also showed that the doxycycline has worthy affinities with SARS-CoV-2 RdRp. As expected, doxycycline effectively inhibited the viral replication of IHU strains of SARS-CoV-2 (IHUMI-3 and IHUMI-6), identified from the hospitalized patients in IHU Méditerranée Infection (IHUMI), Marseille, France. Moreover, doxycycline inhibited the viral load in vitro at both on-entry and after viral entry of IHU variants of SARS-CoV-2. The results suggest that doxycycline exhibits strains-dependant antiviral activity against COVID-19. As a result, the current study concludes that doxycycline may be more effective in combination with other drugs for better COVID-19 treatment efficacy.

In silico approach of naringin as potent phosphatase and tensin homolog (PTEN) protein agonist against prostate cancer.

Prostate cancer (PC) is one of the major impediments affecting men, which leads approximately 31,620 deaths in both developing and developed countries. Although some chemotherapy drugs have been reported for prostate cancer, they are not effective due to the lack of safety, efficacy and low selectivity. Hence, the novel alternative anticancer agents with remarkable effect are highly appreciable. Natural plants contain several bio-active compounds which have been traditionally used for the various medical treatments. Particularly, naringin is a natural bio-active compound commonly found in the citrus fruits, which have shown numerous biological activities. Phosphatase and tensin homolog (PTEN) is a tumor suppressor gene, which activates both lipid phosphates and protein phosphates. The PTEN gene is negative regulator of PI3K/AKT/mTOR pathways, since, this signaling pathway play an essential role in the cell survival, proliferation and migration. In the present in silico investigation, structure based virtual screening, molecular docking, molecular dynamics simulation and Adsorption, Distribution, Metabolism, Excretion (ADME) prediction were employed to determine the binding affinity, stability and drug likeness properties of top ranked screened compounds and naringin, respectively. The results revealed that the complex has good molecular interactions, binding stability (peak between 0.3 and 0.4 nm) and no violations in the Lipinski Rule of 5 in naringin, but the screened compounds violated the drug likeness properties. From the in silico analyses, it is identified that naringin compound might assist in the development of novel therapeutic candidate against prostate cancer. Communicated by Ramaswamy H. Sarma.

Discovery of potent Camkk1 kinase inhibitors through e-pharmacophore and molecular screening approaches.

Diabetes is recognized as a major health problem and according to WHO estimates global prevalence of diabetes is expected to increase from 171 million in 2000 to 366 million in 2030, among which 21.7% will be Indians. The chronic nature of diabetes leads to several metabolic complications like kidney failure, cardiac problems and hypertension, etc.Camkk family members are attractive and emerging targets for the development of anti-diabetic drugs. However, the selectivity of inhibitors is a crucial property as a lack of selectivity could lead to serious adverse effects. STO-609 recently reported the role of Camkks a as potent inhibitor. In this study, Combined Molecular Docking and Pharmacophore Mapping were employed to identify potent lead molecules. E-Pharmacophore based virtual screening was performed against commercially available databases to identify the best lead molecule which was docked with the targets and analyzed for the binding pattern. Also, ADME and density function theory (DFT) studies of the compound were performed and the hits that showed good binding to the active sites and that matched with the pharmacophore models were considered as possible functional molecules against Camkk1. The results from e-pharmacophore based virtual screening and MD simulations evidenced that the top three compounds namely (Lifechemicals_1, Zinc_0910993 and Binding_10131) will be a promising inhibitor for Camkk1 family.Communicated by Ramaswamy H. Sarma.

Molecular evolution, binding site interpretation and functional divergence of aspartate semialdehyde dehydrogenase.

Aspartate Semialdehyde Dehydrogenase (ASDH) is an important enzyme essential for the viability of pathogenic microorganisms. ASDH is mainly involved in amino acid and cell wall biosynthesis of microorganisms, hence it is considered to be a promising target for drug design. This enzyme depicts similar mechanistic function in all microorganisms; although, the kinetic efficiency of an enzyme differs according to their active site residual composition. Therefore, understanding the residual variation and kinetic efficiency of the enzyme would pave new insights in structure-based drug discovery and a novel drug molecule against ASDH. Here, ASDH from Wolbachia endosymbiont of Brugia malayi is used as a prime enzyme to execute evolutionary studies. The phylogenetic analysis was opted to classify 400 sequences of ASDH enzymes based on their structure and electrostatic surfaces. Analysis resulted in 37 monophyletic clades of diverse pathogenic and non-pathogenic organisms. The representative structures of 37 ASDHs from different clades were further deciphered to structural homologues. These enzymes exhibited presence of more positively charged surfaces than negatively charged surfaces in the active site pocket which restrains evolutionary significance. Docking studies of NADP+ with 37 enzymes reveals that site-specific residual variation in the active site pocket modulates the binding affinity (ranges of -13 to -9 kcal/mol). Type-I and Type-II divergence studies show, no significant functional divergence among ASDH, but residual changes were found among the enzyme that modulates the biochemical characteristics and catalytic efficiency. The present study not only explores residual alteration and catalytic variability, it also aids in the design of species-specific inhibitors.Communicated by Ramaswamy H. Sarma.

Atomistic simulation on flavonoids derivatives as potential inhibitors of bacterial gyrase of Staphylococcus aureus.

The bacterial DNA gyrase is an attractive target to identify the novel antibacterial agents. The flavonoid derivatives possess various biological activities such as antimicrobial, anti-inflammatory and anticancer activities. The aim of present study is to identify the potential molecule from flavonoid derivatives against Staphylococcus aureus using atomistic simulation namely Molecular Docking, Quantum Chemical and Molecular Dynamics. The molecules Cpd58, Cpd65 and Cpd70 are identified as potential molecules through molecular docking approaches by exploring through the N - H…O hydrogen bonding interactions with Asn31 and Glu35 of Gyrase B. To confirm the intramolecular charge transfer in the flavonoid derivatives, Frontier Molecular Orbital (FMO) calculation was performed at M06/6-31g(d) level in gas phase. The lowest HOMO-LUMO gap was calculated for Cpd58, Cpd65 and Cpd70 among the selected compounds used in this study. Molecular dynamics simulation were carried out for Cpd58 and Cpd70 for a time period of 50 ns and found to be stable throughout the analysis. Therefore, the identified compounds are found to be a potent inhibitor for GyrB of S. aureus that can be validated by experimental studies. Communicated by Ramaswamy H. Sarma.

Computational identification of potential lead molecules targeting rho receptor of Neisseria gonorrhoeae.

Gonorrhea, one of the sexually transmitted disease caused by a gram negative diplococcus bacteria Neisseria gonorrhoeae. Rho protein is indispensable for bacterial viability due to its versatile functions in physiology apart from RNA dependent transcription termination. Based on conserved function and wider role in several cellular processes, inhibitors specifically targeting Rho proteins are largely in use these days to treat various bacterial infections. In this study, three dimensional structure of Rho protein was modeled using the template protein from E. coli and further the optimized model was simulated for 100 ns to understand the structural stability and compactness. Owing to the therapeutic potential of Rho, traditional structure-based virtual screening was applied to identify potential inhibitors for the selected target. Based on empirical glide scoring functions two potent lead molecules (ChemBridge_6121956 and ChemBridge_5232688) were selected from ChemBridge database. The pharmacokinetic properties of these lead molecules are within the permissible range. DFT descriptor revealed that the lead molecules are more reactive, which also supports the molecular docking studies. The stability of Rho and Rho-inhibitor complexes was studied using molecular dynamics simulation. Parameters include binding free energy calculation, RMSD, RMSF and hydrogen bond analysis depicts the stability of Rho and Rho-inhibitors throughout the simulation. Altogether, the identified lead molecules require further optimization towards the design and development of new antibiotics against N. gonorrhoeae.Communicated by Ramaswamy H. Sarma.

Water Mapping and Scoring Approaches to Predict the Role of Hydration Sites in the Binding Affinity of PAK1 Inhibitors.

AIM: This study aims to develop and establish a computational model that can identify potent molecules for p21-activating kinase 1 (PAK1) Background: PAK1 is a well-established drug target that has been explored for various therapeutic interventions. Control of this protein requires an indispensable inhibitor to curb the structural changes and subsequent activation of signalling effectors responsible for the progression of diseases, such as cancer, inflammatory, viral, and neurological disorders. OBJECTIVE: The study aims to establish a computational model that could identify active molecules which will further provide a platform for developing potential PAK1 inhibitors. METHODS: A congeneric series of 27 compounds were considered for this study, with Ki (nm) covering a minimum of 3 log range. The compounds were developed based on a previously reported Group-I PAK inhibitor, namely G-5555. The 27 compounds were subjected to the SP and XP mode of docking to understand the binding mode, its conformation and interaction patterns. To understand the relevance of biological activity from computational approaches, the compounds were scored against generated water maps to obtain WM/MM ΔG binding energy. Moreover, molecular dynamics analysis was performed for the highly active compound to understand the conformational variability and stability of the complex. We then evaluated the predictable binding pose obtained from the docking studies. RESULTS: From the SP and XP modes of docking, the common interaction pattern with the amino acid residues Arg299 (cation-π), Glu345 (Aromatic hydrogen bond), hinge region Leu347, salt bridges Asp393 and Asp407 was observed, among the congeneric compounds. The interaction pattern was compared with the co-crystal inhibitor FRAX597 of the PAK1 crystal structure (PDB id: 4EQC). The correlation with different docking parameters in the SP and XP modes was insignificant and thereby revealed that the SP and XP's scoring functions could not predict the active compounds. This was due to the limitations in the docking methodology that neglected the receptor flexibility and desolvation parameters. Hence, to recognise the desolvation and explicit solvent effects, as well as to study the Structure-Activity Relationships (SARs) extensively, WaterMap (WM) calculations were performed on the congeneric compounds. Based on displaceable unfavourable hydration sites (HS) and their associated thermodynamic properties, the WM calculations facilitated in understanding the significance of correlation in the folds of activity of highly active (19 and 17), moderately active (16 and 21) and less active (26 and 25) compounds. Furthermore, the scoring function from WaterMap, namely WM/MM, led to a significant R2 value of 0.72 due to a coupled conjunction with MM treatment and displaced unfavourable waters at the binding site. To check the "optimal binding conformation", molecular dynamics simulation was carried out with the highly active compound 19 to explain the binding mode, stability, interactions, solvent-accessible area, etc., which could support the predicted conformation with bioactive conformation. CONCLUSION: This study determined the best scoring function, established SARs and predicted active molecules through a computational model. This will contribute to the development of the most potent PAK1 inhibitors.