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Nelson-Sathi, S.

Publications and source records attributed to Nelson-Sathi, S..

8 recordsLinked to original sources

Structure-based virtual screening and Molecular Dynamic Simulations identified FDA-approved molecules as potential inhibitors against the surface proteins of H1N1

H1N1, a subtype of influenza A virus, remains a global concern due to its ability to cause highly contagious, and fatal infections of the respiratory tract that can lead to seasonal pandemics. Factors such as genetic reassortment and antigenic shift due to the segmented nature of its RNA genome, lead to its rapid evolution that impacts drug and vaccine interactions. Thus, there is growing interest in identifying small-molecules against H1N1 to address the challenges posed by its ever-changing nature and enhance ability to combat the virus. By targeting the surface proteins crucial in the viral life cycle and interactions with host cells, we conducted structure-based virtual screening of 2,471 FDA-approved small molecules against H1N1s hemagglutinin (HA) and neuraminidase (NA) using molecular docking, and molecular dynamic simulations. A binding pocket for HA was identified at the interface of the three protomers, close to the fusion peptide, while in the case of NA the co-crystal ligand binding site was targeted. We identified 5 molecules, namely Econazole, Butoconazole, Miconazole, Isoconazole, and Tioconazole with higher binding affinity to HA and 4 molecules, namely Acarbose, Rutin, Paromomycin, and Idarubicin showing superior binding affinity to NA. Further molecular dynamic simulation of these molecules bound with HA and NA reaffirm the stability of the complexes. These molecules are known to have antifungal and antiviral properties. Thus, this study elucidates the importance of targeting HA and NA and paves the way for repurposing existing antivirals, antibacterials, and antifungals as inhibitors of the H1N1 viral entry into host cells.

bioinformatics↗

A Rapid Bead-Based Assay For Screening Of SARS-CoV-2 Neutralising Antibodies

Quantitative determination of neutralizing antibodies against Severe Acute Respiratory Syndrome Corona Virus-2 (SARS-CoV-2) is paramount in immunodiagnostics, vaccine efficacy testing, and immune response profiling among the vaccinated population. Cost-effective, rapid, easy-to-perform assays are essential to support the vaccine development process and immunosurveillance studies. Here, we describe a bead-based screening assay for S1-neutralization using recombinant fluorescent proteins of hACE2 and SARS-CoV2-S1, immobilized on solid beads employing nanobodies /metal-affinity tags. Nanobody-mediated capture of SARS-CoV-2 - Spike (S1) on agarose beads served as the trap for soluble recombinant ACE2-GFPSpark, inhibited by neutralizing antibody. The first approach demonstrates single-color fluorescent imaging of ACE2-GFPspark binding to His-tagged S1-Receptor Binding Domain (RBD-His) immobilized beads. The second approach is dual-color imaging of soluble ACE2-GFPSpark to S1-Orange Fluorescent Protein (S1-OFPSpark) beads. Both methods showed a good correlation with the gold standard pseudovirion assay and can be adapted to any fluorescent platforms for screening. Life-time imaging of the ACE2-GFPSpark confirmed the interaction of ACE2 and S1-OFPSpark on beads. The self-renewable source of secreted recombinant proteins from stable cells and its direct use without necessitating purification renders the platform a cost-effective and rapid one than the popular pseudovirion assay and live virus-based assays. Any laboratory with minimum expertise can rapidly perform this bead assay for neutralizing antibody detection using stable engineered cells.

molecular biology↗

Structural and Functional Implications of Non-synonymous Mutations in the Spike protein of 2,954 SARS-CoV-2 Genomes

Protein-protein interactions between virus and host are crucial for infection. SARS-CoV-2, the causative agent of COVID-19 pandemic is an RNA virus prone to mutations. Formation of a stable binding interface between the Spike (S) protein Receptor Binding Domain (RBD) of SARS-CoV-2 and Angiotensin-Converting Enzyme 2 (ACE2) of host actuates viral entry. Yet, how this binding interface evolves as virus acquires mutations during pandemic remains elusive. Here, using a high fidelity bioinformatics pipeline, we analysed 31,403 SARS-CoV-2 genomes across the globe, and identified 444 non-synonymous mutations that cause 49 distinct amino acid substitutions in the RBD. Molecular phylogenetic analysis suggested independent emergence of these RBD mutants during pandemic. In silico structure modelling of interfaces induced by mutations on residues which directly engage ACE2 or lie in the near vicinity revealed molecular rearrangements and binding energies unique to each RBD mutant. Comparative structure analysis using binding interface from mouse that prevents SARS-CoV-2 entry uncovered minimal molecular determinants in RBD necessary for the formation of stable interface. We identified that interfacial interaction involving amino acid residues N487 and G496 on either ends of the binding scaffold are indispensable to anchor RBD and are well conserved in all SARS-like corona viruses. All other interactions appear to be required to locally remodel binding interface with varying affinities and thus may decide extent of viral transmission and disease outcome. Together, our findings propose the modalities and variations in RBD-ACE2 interface formation exploited by SARS-CoV-2 for endurance. ImportanceCOVID-19, so far the worst hit pandemic to mankind, started in January 2020 and is still prevailing globally. Our study identified key molecular arrangements in RBD-ACE2 interface that help virus to tolerate mutations and prevail. In addition, RBD mutations identified in this study can serve as a molecular directory for experimental biologists to perform functional validation experiments. The minimal molecular requirements for the formation of RBD-ACE2 interface predicted using in silico structure models may help precisely design neutralizing antibodies, vaccines and therapeutics. Our study also proposes the significance of understanding evolution of protein interfaces during pandemic.

evolutionary biology↗

Evolutionary route of resistant genes in Staphylococcus aureus

Multi-drug resistant S. aureus is a leading concern worldwide. Coagulase-Negative Staphylococci (CoNS) are claimed to be the reservoir and source of important resistant elements in S. aureus. However, the origin and evolutionary route of resistant genes in S. aureus are still remaining unknown. Here, we performed a detailed phylogenomic analysis of 152 completely sequenced S. aureus strains in comparison with 7,529 non-S. aureus reference bacterial genomes. Our results reveals that S. aureus has a large open pan-genome where 97 (55%) of its known resistant related genes belonging to its accessory genome. Among these genes, 47 (27%) were located within the Staphylococcal Cassette Chromosome (SCCmec), a transposable element responsible for resistance against major classes of antibiotics including beta-lactams, macrolides and aminoglycosides. However, the physically linked mec-box genes (MecA-MecR-MecI) that are responsible for the maintenance of SCCmec elements is not unique to S. aureus, instead it is widely distributed within Staphylococcaceae family. The phyletic patterns of SCCmec encoded resistant genes in Staphylococcus species are significantly different from that of its core genes indicating frequent exchange of these genes between Staphylococcus species. Our in-depth analysis of SCCmec resistant gene phylogenies reveals that genes such as blaZ, ble, kmA and tetK that are responsible for beta-lactam, bleomycin, kanamycin and tetracycline resistance in S. aureus were laterally transferred from non-Staphylococcus sources. In addition, at least 11 non-SCCmec encoded resistant genes in S. aureus, mostly present in plasmid are laterally acquired from distantly related species. Our study evidently shows that gene transfers played a crucial role in shaping the evolution of antibiotic resistance in S. aureus.

evolutionary biology↗

Anomalous phylogenetic behavior of ribosomal proteins in metagenome assembled genomes

Metagenomic studies have claimed the existence of novel lineages with unprecedented properties never before observed in prokaryotes. Such lineages include Asgard archaea1-3, which are purported to represent archaea with eukaryotic cell complexity, and the Candidate Phyla Radiation (CPR), a novel domain level taxon erected solely on the basis of metagenomic data4. However, it has escaped the attention of most biologists that these metagenomic sequences are not assembled into genomes by sequence overlap, as for cultured archaea and bacteria. Instead, short contigs are sorted into computer files by a process called binning in which they receive taxonomic assignment on the basis of sequence properties like GC content, dinucleotide frequencies, and stoichiometric co-occurrence across samples. Consequently, they are not genome sequences as we know them, reflecting the gene content of real organisms. Rather they are metagenome assembled genomes (MAGs). Debates that Asgard data are contaminated with individual eukaryotic sequences5-7 are overshadowed by the more pressing issue that no evidence exists to indicate that any sequences in binned Asgard MAGs actually stem from the same chromosome, as opposed to simply stemming from the same environment. Here we show that Asgard and CPR MAGs fail spectacularly to meet the most basic phylogenetic criterion8 fulfilled by genome sequences of all cultured prokaryotes investigated to date: the ribosomal proteins of Asgard and CPR MAGs do not share common evolutionary histories. Their phylogenetic behavior is anomalous to a degree never observed with genomes of real organisms. CPR and Asgard MAGs are binning artefacts, assembled from environments where up to 90% of the DNA is from dead cells9-12. Asgard and CPR MAGs are unnatural constructs, genome-like patchworks of genes that have been stitched together into computer files by binning.

evolutionary biology↗

Insights into the bacterial profiles and resistome structures following severe 2018 flood in Kerala, South India

Extreme flooding is one of the major risk factors for human health, and it can significantly influence the microbial communities and enhance the mobility of infectious disease agents within its affected areas. The flood crisis in 2018 was one of the severe natural calamities recorded in the southern state of India (Kerala) that significantly affected its economy and ecological habitat. We utilized a combination of shotgun metagenomics and bioinformatics approaches for understanding microbiome disruption and the dissemination of pathogenic and antibiotic-resistant bacteria on flooded sites. Here we report, altered bacterial profiles at the flooded sites having 77 significantly different bacterial genera in comparison with non-flooded mangrove settings. The flooded regions were heavily contaminated with faecal contamination indicators such as Escherichia coli and Enterococcus faecalis and resistant strains of Pseudomonas aeruginosa, Salmonella Typhi/Typhimurium, Klebsiella pneumoniae, Vibrio cholerae and Staphylococcus aureus. The resistome of the flooded sites contains 103 resistant genes, of which 38% are encoded in plasmids, where most of them are associated with pathogens. The presence of 6 pathogenic bacteria and its susceptibility to multiple antibiotics including ampicillin, chloramphenicol, kanamycin and tetracycline hydrochloride were confirmed in flooded and post-flooded sites using traditional culture-based analysis followed by 16S rRNA sequencing. Our results reveal altered bacterial profile following a devastating flood event with elevated levels of both faecal contamination indicators and resistant strains of pathogenic bacteria. The circulation of raw sewage from waste treatment settings and urban area might facilitate the spreading of pathogenic bacteria and resistant genes.

microbiology↗

Adaptation to life on land at 21% O2 via transition from ferredoxin- to NADH-dependent redox balance

Pyruvate:ferredoxin oxidoreductase (PFO) and iron only hydrogenase ([Fe]-HYD) are common enzymes among eukaryotic microbes that inhabit anaerobic niches. Their function is to maintain redox balance by donating electrons from food oxidation via ferredoxin (Fd) to protons, generating H2 as a waste product. Operating in series, they constitute a soluble electron transport chain of one-electron transfers between FeS clusters. They fulfill the same function -- redox balance -- served by two electron-transfers in the NADH- and O2-dependent respiratory chains of mitochondria. Although they possess O2-sensitive FeS clusters, PFO, Fd and [Fe]-HYD are also present among numerous algae that produce O2. The evolutionary persistence of these enzymes among eukaryotic aerobes is traditionally explained as enabling facultative anaerobic growth. Here we show that algae express enzymes of anaerobic energy metabolism at ambient O2 levels (21% v/v), Chlamydomonas reinhardtii expresses them with diurnal regulation. High O2 environments arose on Earth only some [~]450 million years ago. Gene presence absence and gene expression data indicate that during the transition to high O2 environments and terrestrialization, diverse algal lineages retained enzymes of Fd-dependent one-electron based redox balance, while the land plant and land animal lineages underwent irreversible specialization to redox balance involving the O2-insensitive two-electron carrier NADH.\n\nHighlights- Algae express enzymes of anaerobic metabolism in 21% [v/v] O2 atmosphere, independent of anaerobiosis\n- Retention of a plastid-encoded NADH dehydrogenase-like (NDH) was likely a prerequisite for the transition to life on land\n- Terrestrialization and adaption to high O2 is accompanied by a shift to redox balance at higher midpoint potentials\n- Eukaryotes adapted to high O2 life on land via specialization to two-electron based redox balance

evolutionary biology↗

Count does not recover major events of gene flux in real biological data

In prokaryotes, known mechanisms of lateral gene transfer (transformation, transduction, conjugation and gene transfer agents) generate new combinations of genes among chromosomes during evolution. In eukaryotes, whose host lineage is descended from archaea, lateral gene transfer from organelles to the nucleus occurs at endosymbiotic events. Recent genome analyses studying gene distributions have uncovered evidence for sporadic, discontinuous events of gene transfer from bacteria to archaea during evolution. Other studies have used traditional birth-and-death phylogenetic models to investigate prokaryote genome evolution to claim that gene transfer to archaea was continuous during evolution, rather than involving occasional periodic mass gene influx events. Here we test the ability of Count, a birth-and-death based program, to recover known events of mass acquisition and differential loss using plastid genomes and eukaryotic protein families that were acquired from plastids. Count showed a strong bias towards reconstructed histories having gene acquisitions distributed uniformly across the tree. Sometimes as many as nine different acquisitions by plastid DNA were inferred for the same protein family. That is, Count recovered gradual and continuous lateral gene transfer among lineages, even when massive gains followed by gradual differential loss is the true evolutionary process that generated the gene distribution data.

evolutionary biology↗