Impact of Fe + 2 ions on structural integrity of A0A6P1CI42_RHITR NifA protein from Rhizobium tropici strain CIAT 899.

A0A6P1CI42_RHITR, a protein originating from Rhizobium tropici strain CIAT 899, has emerged as a key player in leguminous plant symbiosis and nitrogen fixation processes. Understanding the intricate details of its structure and function holds immense significance for unraveling the molecular mechanisms underlying its biological activities. In this study, we employed molecular modeling and molecular dynamics (MD) simulations to investigate the A0A6P1CI42_RHITR protein, with a specific emphasis on the influence of Fe-atoms, linker structural integrity, and conformational changes within the GAF domain. Our findings unveiled noteworthy conformational changes in the A0A6P1CI42_RHITR protein, particularly within the GAF domain, when Fe-atoms were present compared to its apo form. Significant conformational rearrangements after an initial 20 ns, accompanied by the opening of the ligand substrate accommodating loop in the GAF domain influenced by Fe-atoms was observed. At the residue level, the investigation revealed substantial activity variations in individual residues, particularly in those contributing to the GAF domain from positions 51 to 223. Intriguingly, the presence of Fe-atoms led to controlled movement of conserved cysteine residues at positions 467 and 472, indicating a correlation between interlinker domain motion and the activity of the GAF domain loop responsible for substrate accommodation. Moreover, in the presence of Fe-atoms, the distance between Cys467 and Cys472 residues was maintained, ensuring the overall structural integrity of the interdomain loop necessary for protein activation. Conversely, in the apo form, a sudden flip motion of cysteine residues' thiol groups was observed, leading to a loss of structural integration. Overall, our study utilizing molecular modeling and MD simulations offers valuable insights into the structural dynamics and functional implications of the A0A6P1CI42_RHITR protein.Communicated by Ramaswamy H. Sarma.

In-silico anti-inflammatory potential of guaiane dimers from Xylopia vielana targeting COX-2.

Natural products of herbal origin are prodigious to display diverse pharmacological activities. In the present study, five guaiane-type sesquiterpene dimers, xylopidimers A - E (1-5), isolated from Xylopia vielana species were tested against COX-2 protein target (PDB: 1CX2), a potent target for anti-inflammatory agents. To better understand the pharmacological properties of all these compounds, in this work, a systemic in silico study was performed on xylopidimers A-E using molecular docking, ADMET analysis and MD simulations. During ADMET predictions the two compounds xylopidimer C, D displayed best results as compared to others. The compound xylopidimer C was further evaluated for its MD simulations and its molecular interactions with COX2 complex showed clear interactions with active gorge of the enzyme through hydrogen bonding as well as hydrophobic contacts. The xylopidimer C has shown the best binding potential with -10.57Kcal/mol energy with 17.92 nano molar of predicted inhibition constant better than Ibuprofen and Felbinac. These findings provide enough significant information for designing and developing novel targeted base anti-inflammatory drugs from guaiane dimers.

Impact of F80M and F83M mutations on the functionality of fluoride ion channel elucidated in microsecond level molecular dynamic simulation.

Fluoride ion channels of the Fluc family plays a critically important role in combating environmental fluoride toxicity. As per the crystal structure of these fluoride ion channels, the pore region is densely packed with a series of hydrogen bond donating residues arranged in a ladder fashion creating an ion conducting pathway. In earlier studies, it was revealed that although the ion conducting pathway polarity is highly conserved, however the functionality of the channel protein depends on several residues at particular positions. While, a threonine at end of the pore is critically important in forming initial interactions, two phenylalanines at the central region coordinate F- transportation through the channel. It was also revealed that these two phenylalanines cannot be substituted by any other aromatic, polar or non-polar residues without hindering the functionality with exception of methionine. In another study, it was revealed that these two phenylalanines F80 and F83 when mutated with methionine; F80M lead to active state, while the F83M has lead to inactivity of F- anion conductivity. However, the exact atomic level detailing on how exactly these mutations have impacted the conductivity remained elusive. In this scenario, in this present study, we have modeled these two mutations and performed a microsecond level simulation on each mutation compared with wild type towards understanding the atomic level detailing revealing several insights on what exactly happening at these residues responsible for the selective conductivity of F- ions.Communicated by Ramaswamy H. Sarma.

Role of Thr199 residue in human ß-carbonic anhydrase-II pH-dependent activity elucidated by microsecond simulation analysis.

Carbonic anhydrases catalyze the reversible hydration of carbon dioxide to form bicarbonate, a reaction required for many functions such as carbon assimilation, pH acid-base homeostasis, respiration and photosynthesis via a zinc-hydroxide mechanism for carbon dioxide hydration. In earlier studies, it was revealed that Carbonic anhydrases are inactive at pH 7.5 and active at pH 8.4. This steep pH dependence for its activity led us to design this work to understand its mode of action at atomic level detail. In our microsecond simulation based analysis, it was revealed that the interaction between Glu106 and Thr199 plays a critically important role in its activity. Thr199 co-ordinated loop movement was observed to be acting as a lid, with 'open' and 'close' mechanism for substrate entry to the core of the catalytic site, where Zn-ion resides and executes its carbon dioxide hydration mechanism. On the other hand, decline in the total secondary structural elements percentage in the protein was observed in correspondence to the pH condition change. The α-helices between Thr125-Gly145 and Val150-Lys170 residues were especially noticed to be losing their structural integrity responsible for formation of dimer and tetramers. In conclusion, our analysis showed that the interaction between Glu106 and Thr199 is crucial for maintaining the structural integrity of the Thr199 coordinated loop, responsible for allowing substrate towards the catalytic site.Communicated by Ramaswamy H. Sarma.

CDH5, a Possible New Candidate Gene for Genetic Testing of Lymphedema.

Background: Expressed by endothelial cells, CDH5 is a cadherin involved in vascular morphogenesis and in the maintenance of vascular integrity and lymphatic function. The main purpose of our study was to identify distinct variants of the CDH5 gene that could be associated with lymphatic malformations and predisposition for lymphedema. Methods and Results: We performed Next Generation Sequencing of the CDH5 gene in 235 Italian patients diagnosed with lymphedema but who tested negative for variants in known lymphedema genes. We detected six different variants in CDH5 five missense and one nonsense. We also tested available family members of the probands. For family members who carried the same variant as the proband, we performed lymphoscintigraphy to detect any lymphatic system abnormalities. Variants were modeled in silico. The results showed that CDH5 variants may contribute to the onset of lymphedema, although further in vitro studies are needed to confirm this hypothesis. Conclusions: Based on our findings, we propose CDH5 as a new gene that could be screened in patients with lymphedema to gather additional evidence.

Possible Role of the RORC Gene in Primary and Secondary Lymphedema: Review of the Literature and Genetic Study of Two Rare Causative Variants.

Background: RAR-related Orphan Receptor C (RORC) is a DNA-binding transcription factor and the key transcription factor responsible for differentiation of T helper 17 cells. The RORC gene plays a role in lymphoid organogenesis, thymopoiesis, and lymph node organogenesis. The aim of our study was to determine the possible role of RORC in the development of lymphatic system malformations by combining data from the scientific literature and next-generation sequencing of RORC in lymphedema patients negative for known causative genes. Methods and Results: We sequenced RORC in 235 lymphedema patients negative for known lymphedema-associated genes. We found two probands carrying nonsense RORC variants. Conclusions: We show that RORC is important for normal function of the lymphatic system and that a rare variant with a possible causative effect may imply predisposition for lymphedema.

NOTCH1: Review of its role in lymphatic development and study of seven families with rare pathogenic variants.

BACKGROUND: We developed a Next-Generation-Sequencing (NGS) protocol to screen the most frequent genetic variants related to lymphedema and a group of candidate genes. The aim of the study was to find the genetic cause of lymphedema in the analyzed patients. METHODS: We sequenced a cohort of 246 Italian patients with lymphatic malformations. In the first step, we analyzed genes known to be linked to lymphedema: 235 out of 246 patients tested negative for the most frequent variants and underwent testing for variants in a group of candidate genes, including the NOTCH1 gene, selected from the database of mouse models. We also performed in silico analysis to observe molecular interactions between the wild-type and the variant amino acids and other protein residues. RESULTS: Seven out of 235 probands, five with sporadic and two with familial lymphedema, were found to carry rare missense variants in the NOTCH1 gene. CONCLUSIONS: Our results propose that NOTCH1 could be a novel candidate for genetic predisposition to lymphedema.

Segregation Analysis of Rare NRP1 and NRP2 Variants in Families with Lymphedema.

Neuropilins are transmembrane coreceptors expressed by endothelial cells and neurons. NRP1 and NRP2 bind a variety of ligands, by which they trigger cell signaling, and are important in the development of lymphatic valves and lymphatic capillaries, respectively. This study focuses on identifying rare variants in the NRP1 and NRP2 genes that could be linked to the development of lymphatic malformations in patients diagnosed with lymphedema. Two hundred and thirty-five Italian lymphedema patients, who tested negative for variants in known lymphedema genes, were screened for variants in NRP1 and NRP2. Two probands carried variants in NRP1 and four in NRP2. The variants of both genes segregated with lymphedema in familial cases. Although further functional and biochemical studies are needed to clarify their involvement with lymphedema and to associate NRP1 and NRP2 with lymphedema, we suggest that it is worthwhile also screening lymphedema patients for these two new candidate genes.

Mutations in the ARAP3 Gene in Three Families with Primary Lymphedema Negative for Mutations in Known Lymphedema-Associated Genes.

BACKGROUND: ARAP3 is a small GTPase-activating protein regulator, which has important functions in lymphatic vessel organogenesis and modulation of cell adhesion and migration. Mutations in the ARAP3 gene are associated with impaired lymphatic vessel formation. OBJECTIVE: The aim of our study was to determine the genotypes of lymphedema patients in relation to variants in the ARAP3 gene in order to explore its role in the development of lymphedema. METHODS AND RESULTS: We applied next-generation sequencing to DNA samples of a cohort of 246 Italian patients with lymphatic malformations. When we tested probands for known lymphedema genes, 235 out of 246 were negative. Retrospectively, we tested the DNA of these 235 patients for new candidate lymphedema-associated genes, including ARAP3. Three out of 235 probands proved to carry rare missense heterozygous variants in ARAP3. In the case of two families, other family members were also tested and proved negative for the ARAP3 variant, besides being unaffected by lymphedema. According to in silico analysis, alterations due to these variants have a significant impact on the overall structure and stability of the resulting proteins. CONCLUSIONS: Based on our results, we propose that variants in ARAP3 could be included in genetic testing for lymphedema.

TIE1 as a Candidate Gene for Lymphatic Malformations with or without Lymphedema.

TIE1 is a cell surface protein expressed in endothelial cells. Involved in angiogenesis and lymphangiogenesis, including morphogenesis of lymphatic valves, TIE1 is important for lymphatic system functional integrity. The main purpose of this study was to identify different variants in the TIE1 gene that could be associated with lymphatic malformations or dysfunction and predisposition for lymphedema. In a cohort of 235 Italian lymphedema patients, who tested negative for variants in known lymphedema genes, we performed a further test for new candidate genes, including TIE1. Three probands carried different variants in TIE1. Two of these segregated with lymphedema or lymphatic dysfunction in familial cases. Variants in TIE1 could contribute to the onset of lymphedema. On the basis of our findings, we propose TIE1 as a candidate gene for comprehensive genetic testing of lymphedema.

Characterization, molecular docking, dynamics simulation and metadynamics of kisspeptin receptor with kisspeptin.

We report molecular characterization of the kisspeptin receptor (kiss1r), an essential gatekeeper for reproduction and onset of puberty in vertebrates. The full-length cDNA sequence of kiss1r is 1786bp which consist of 5' UTR (untranslated region) 261bp, 3' UTR of 424bp and open reading frame of 1101 encoding a putative protein of 366 amino acids. Basal tissue expression pattern of kiss1r mRNA revealed that it is mainly expressed in the brain and testis. We also report the structure of the kiss1r, along with plausible activation mechanism of this receptor by kisspeptin using computational modelling and dynamic simulation approach of multiple 100ns of timescale. A present modelling and simulations studies shed light on the molecular level of interaction, suggesting that direct hydrogen bonds between ASN4, SER5, GLY7, ARG9 and PHE10 of kisspeptin and TRP7, ASN8, GLU11, ILE17, ASN19 and TYR183 of kiss1r could be crucial role players in initial binding of receptor and the kisspeptin towards allosteric modulatory effects of kisspeptin on the receptor. To the best our knowledge, this is the first report on computational modelling and molecular dynamic simulations of kiss1r in animals shedding light on its possible mode of activation.

A Comprehensive In Silico Analysis on the Structural and Functional Impact of SNPs in the Congenital Heart Defects Associated with NKX2-5 Gene-A Molecular Dynamic Simulation Approach.

Congenital heart defects (CHD) presented as structural defects in the heart and blood vessels during birth contribute an important cause of childhood morbidity and mortality worldwide. Many Single nucletotide polymorphisms (SNPs) in different genes have been associated with various types of congenital heart defects. NKX 2-5 gene is one among them, which encodes a homeobox-containing transcription factor that plays a crucial role during the initial phases of heart formation and development. Mutations in this gene could cause different types of congenital heart defects, including Atrial septal defect (ASD), Atrial ventricular block (AVB), Tetralogy of fallot and ventricular septal defect. This highlights the importance of studying the impact of different SNPs found within this gene that might cause structural and functional modification of its encoded protein. In this study, we retrieved SNPs from the database (dbSNP), followed by identification of potentially deleterious Non-synonymous single nucleotide polymorphisms (nsSNPs) and prediction of their effect on proteins by computational screening using SIFT and Polyphen. Furthermore, we have carried out molecular dynamic simulation (MDS) in order to uncover the SNPs that would cause the most structural damage to the protein altering its biological function. The most important SNP that was found using our approach was rs137852685 R161P, which was predicted to cause the most damage to the structural features of the protein. Mapping nsSNPs in genes such as NKX 2-5 would provide valuable information about individuals carrying these polymorphisms, where such variations could be used as diagnostic markers.

Pharmacophore feature-based virtual screening for finding potent GSK-3 inhibitors using molecular docking and dynamics simulations.

Glycogen synthase kinase-3 (GSK-3) is a multitasking serine/threonine protein kinase, which is associated with the pathophysiology of several diseases such as diabetes, cancer, psychiatric and neurodegenerative diseases. Tideglusib is a potent, selective, and irreversible GSK-3 inhibitor that has been investigated in phase II clinical trials for the treatment of progressive supranuclear palsy and Alzheimer's disease. In the present study, we performed pharmacophore feature-based virtual screening for identifying potent targetspecific GSK-3 inhibitors. We found 64 compounds that show better GSK-3 binding potentials compared with those of Tideglusib. We further validated the obtained binding potentials by performing 20-ns molecular dynamics simulations for GSK-3 complexed with Tideglusib and with the best compound found via virtual screening in this study. Several interesting molecular-level interactions were identified, including a covalent interaction with Cys199 residue at the entrance of the GSK-3 active site. These findings are expected to play a crucial role in the binding of target-specific GSK-3 inhibitors.

Insights from the predicted structural analysis of carborane substituted withaferin A with Indoleamine - 2,3-dioxygenase as a potent inhibitor.

Indoleamine-2,3-dioxygenase (IDO) an immunoregulatory enzyme and emerging as a new therapeutic drug target for the treatment of cancer. Carboranes, an icosahedral arrangement of eleven boron atoms plus one carbon atom with unique pharmacological properties such low toxicity, isosterism with phenyl ring and stability to hydrolysis. On the other hand, carboranes are known to increase the interaction of ligand with non-polar region of the protein provides an excellent platform to explore these carboranes towards designing and development of novel, potent and target specific drug candidates with further enhanced binding affinities. Despite of their many potential applications, molecular modeling studies of carborane-substituted ligands with macromolecules have been rarely reported. Previously, we have demonstrated the promising high binding affinity of Withaferin-A (WA) for IDO. In this present study, we investigated the effect of carborane substitutions on WA compound towards developing novel analogs for target specific IDO inhibition with better potency. Interesting docked poses and molecular interactions for the carborane substituted WA ligands were elucidated. Based on our In-silico studies, carborane substituted at various position of WA has shown enhanced binding affinity towards IDO, worth of considering for further studies.

Molecular docking based screening of novel designed chalcone series of compounds for their anti-cancer activity targeting EGFR kinase domain.

Epidermal growth factor receptors (EGFR) are critical for the growth of many tumors and expressed at high levels in about one third of epithelial cancers. Hence, blockade of the binding sites for EGFR has been hypothesized as an effective anti-cancer therapy. Chalcone derivative compounds have been shown to be highly effective anti-cancer agents, however there are still so many novel derivatives possible, one of which might get us the best targeted EGFR inhibitor. In this effort directed towards the discovery of novel, potent anti-tumor agents for the treatment of cancer, in the present study a library of novel chalcone series of compounds has been designed and evaluated for their anti-cancer activity targeting EGFR kinase domain using various computational approaches. Among the twenty five novel designed chalcone series of compounds, all of them have found to be successfully docking inside the active binding domain of EGFR receptor target with a binding energy in a range of -6.10 to -9.25 Kcal/mol with predicted IC50 value range of 33.50 micor molar to 164.66 nano molar respectively. On the other hand, calculated 2DQSAR molecular descriptor properties of the compounds showed promising ADME parameters and found to be well in compliance with Lipinski׳s rule of five. Among all the twenty five compounds tested, compound 21 ((2E)-3-(anthracen-9-yl)-1-phenylprop-2-2n-1- one) was found to be the best lead like molecule with a binding energy of -9.25 kcal/mol with predicted IC50 value of 164.66 nano molar. Conclusively, novel designed compound 21 of the present study have shown promising anti-cancer potential worth considering for further evaluations.

Molecular docking and dynamic simulation studies evidenced plausible immunotherapeutic anticancer property by Withaferin A targeting indoleamine 2,3-dioxygenase.

Indoleamine 2,3-dioxygenase (IDO) is emerging as an important new therapeutic drug target for the treatment of cancer characterized by pathological immune suppression. IDO catalyzes the rate-limiting step of tryptophan degradation along the kynurenine pathway. Reduction in local tryptophan concentration and the production of immunomodulatory tryptophan metabolites contribute to the immunosuppressive effects of IDO. Presence of IDO on dentritic cells in tumor-draining lymph nodes leading to the activation of T cells toward forming immunosuppressive microenvironment for the survival of tumor cells has confirmed the importance of IDO as a promising novel anticancer immunotherapy drug target. On the other hand, Withaferin A (WA) - active constituent of Withania Somnifera ayurvedic herb has shown to be having a wide range of targeted anticancer properties. In the present study conducted here is an attempt to explore the potential of WA in attenuating IDO for immunotherapeutic tumor arresting activity and to elucidate the underlying mode of action in a computational approach. Our docking and molecular dynamic simulation results predict high binding affinity of the ligand to the receptor with up to -11.51 kcal/mol of energy and 3.63 nM of IC50 value. Further, de novo molecular dynamic simulations predicted stable ligand interactions with critically important residues SER167; ARG231; LYS377, and heme moiety involved in IDO's activity. Conclusively, our results strongly suggest WA as a valuable small ligand molecule with strong binding affinity toward IDO.

Computational repositioning of ethno medicine elucidated gB-gH-gL complex as novel anti herpes drug target.

BACKGROUND: Herpes viruses are important human pathogens that can cause mild to severe lifelong infections with high morbidity. They remain latent in the host cells and can cause recurrent infections that might prove fatal. These viruses are known to infect the host cells by causing the fusion of viral and host cell membrane proteins. Fusion is achieved with the help of conserved fusion machinery components, glycoproteins gB, heterodimer gH-gL complex along with other non-conserved components. Whereas, another important glycoprotein gD without which viral entry to the cell is not possible, acts as a co-activator for the gB-gH-gL complex formation. Thus, this complex formation interface is the most promising drug target for the development of novel anti-herpes drug candidates. In the present study, we propose a model for binding of gH-gL to gB glycoprotein leading from pre to post conformational changes during gB-gH-gL complex formation and reported the key residues involved in this binding activity along with possible binding site locations. To validate the drug targetability of our proposed binding site, we have repositioned some of the most promising in vitro, in vivo validated anti-herpes molecules onto the proposed binding site of gH-gL complex in a computational approach. METHODS: Hex 6.3 standalone software was used for protein-protein docking studies. Arguslab 4.0.1 and Accelrys® Discovery Studio 3.1 Visualizer softwares were used for semi-flexible docking studies and visualizing the interactions respectively. Protein receptors and ethno compounds were retrieved from Protein Data Bank (PDB) and Pubchem databases respectively. Lipinski's Filter, Osiris Property Explorer and Lazar online servers were used to check the pharmaceutical fidelity of the drug candidates. RESULTS: Through protein-protein docking studies, it was identified that the amino acid residues VAL342, GLU347, SER349, TYR355, SER388, ASN395, HIS398 and ALA387 of gH-gL complex play an active role in its binding activity with gB. Semi flexible docking analysis of the most promising in vitro, in vivo validated anti-herpes molecules targeting the above mentioned key residues of gH-gL complex showed that all the analyzed ethno medicinal compounds have successfully docked into the proposed binding site of gH-gL glycoprotein with binding energy range between -10.4 to -6.4 K.cal./mol. CONCLUSIONS: Successful repositioning of the analyzed compounds onto the proposed binding site confirms the drug targetability of gH-gL complex. Based on the free binding energy and pharmacological properties, we propose (3-chloro phenyl) methyl-3,4,5 trihydroxybenzoate as worth a small ethno medicinal lead molecule for further development as potent anti-herpes drug candidate targeting gB-gH-gL complex formation interface.