Biology subjects

Palur, R. V.

Publications and source records attributed to Palur, R. V..

3 recordsLinked to original sources

bioRxiv2025

N153-linked glycans on envelope protein protect orthoflaviviruses from antibody-mediated clearance

The envelope (E) protein of dengue virus (DENV) is glycosylated at two highly conserved asparagine (N) sites (N67 and N153). The role and importance of these N-linked glycans in DENV pathogenesis has been elusive. Here, we report the critical role of N153-linked glycans on E protein in preventing antibody-mediated viral clearance. A DENV2 mutant lacking N153-linked glycans (N153Q mutant) was engineered and found to be mildly impaired in vitro but drastically attenuated in a symptomatic mouse model of severe dengue, as evidenced by accelerated viral clearance. In B cell-deficient mouse models, N153Q mutant displayed parental virulence and viremia profile. Homologous and heterologous passive transfers of purified IgM from infected B cell-proficient mice into B cell-deficient mice demonstrated the role of N153Q-specific IgM in N153Q attenuation and accelerated clearance, while WT DENV was unaffected by IgM from both WT- and N153Q-infected mice. Furthermore, in vitro neutralization assay supported that the accelerated clearance of N153Q mutant in mice was mediated by non-neutralizing IgM. Furthermore, using plasma samples from convalescent dengue patients and monoclonal antibodies, in vitro neutralization assays showed that N153Q virus was more susceptible than WT to IgG-mediated neutralization. Glycoproteomics combined with molecular dynamics (MD) simulations revealed that glycan composition on E protein influenced IgG binding. Our findings were extended to all DENV serotypes and ZIKV, hence supporting that the N153 glycans-mediated immune evasion strategy is conserved across orthoflaviviruses.

microbiology↗

bioRxiv2024

Molecular Dynamics Trajectory Analysis of Permeation (MDTAP): A tool to analyze permeation events across membrane proteins

Background and ObjectiveMolecular dynamics (MD) simulations are indispensable and versatile in capturing the time-dependent conformational changes of biomolecules to shed light on the concomitant biological processes. MD is used to provide critical mechanistic insights into the transportation of solvent/solute/drug molecules across protein channels embedded in a membrane bilayer. The huge size and volume of the MD trajectories of a membrane-embedded system provide challenges in the analyses of membrane permeation events. Thus, a software, Molecular Dynamics Trajectory Analysis of Permeation (MDTAP), is presented here to analyze the permeation events across membrane-embedded proteins and nucleic acids automatically. MethodsA software is developed here to automatically detect the permeation events across the channels irrespective of their shape and size and the type of solute molecules from the MD trajectories. MDTAP employs bash scripts to fetch information about the permeation, residence time, and diffusion of the molecules of interest in a Linux/Mac-based environment. The source code of MDTAP is freely available to the public, along with installation and usage information on GitHub (attached as supplementary for the review process and will be made accessible to the public through the following link upon acceptance for publication: https://github.com/MBL-lab/MDTAP). ResultsThe efficiency of MDTAP is demonstrated here by considering the MD trajectories of 2 water-conducting channels as test cases: E. coli outer membrane protein Wzi and E. coli Aquaporin Z. The dimensions of the channels and their capacity to accommodate and conduct water, the number of permeating water molecules along with the path traced and time taken to cross the channel is validated. ConclusionIn summary, the graphical representation of the time-dependent behavior of the solute/solvent permeation events corresponding to an MD trajectory in MDTAP allows the user to easily visualize the mechanism of permeation, including the localization of the permeating molecule (if any) and permeating path. Thus, MDTAP immensely reduces the difficult task of manually analyzing solute/solvent permeations from the bulk MD trajectories. Such a simplistic representation of permeation events across the protein transporters helps in the design of drug molecules to treat the associated diseases. Further, MDTAP is also designed to characterize the permeation events across artificial nucleic acid channels, considering their importance in recent times.

biophysics↗

bioRxiv2020

Dengue virus strain 2 capsid protein switches the annealing pathway and reduces the intrinsic dynamics of the conserved 5' untranslated region

The capsid protein of Dengue Virus strain 2 (DENV2C) is a structural protein with RNA chaperone activity that promotes multiple nucleic acid structural rearrangements, critical for transcription of the single-stranded positive-sense DENV2 genomic RNA. Annealing of the conserved 5 untranslated region (5UTR) to either its complementary sequence or to the 3 untranslated region (3UTR) occurs during (+)/(-) ds-RNA formation and (+) RNA circularization, respectively, both essential steps during DENV RNA replication. We investigated the effect of DENV2C on the annealing mechanism of two hairpin structures from the 5UTR region (21-nt upstream AUG region (5UAR) and 23-nt capsid-coding hairpin (5cHP)) to their complementary sequences during (+)/(-) ds-RNA formation and (+) RNA circularization. Using fluorescence spectroscopy, DENV2C was found to switch annealing reactions nucleated mainly through kissing-loop intermediates to stem-stem interactions during (+)/(-) ds-RNA formation while it promotes annealing mainly through kissing-loop interactions during the (+) RNA circularization. Using FRET-FCS and trFRET, we determined that DENV2C exerts RNA chaperone activities by modulating intrinsic dynamics and by reducing the kinetically trapped unfavorable conformations of the 5UTR sequence. Thus, DENV2C is likely to facilitate genome folding into functional conformations required for replication, playing a role in modulating (+)/(-) ds-RNA formation and (+) RNA circularization.

molecular biology↗