Biology subjects

Zuzic, L.

Publications and source records attributed to Zuzic, L..

5 recordsLinked to original sources

bioRxiv2024

Creating Coarse-Grained Systems with COBY: Towards Higher Accuracy in Membrane Complexity

Current trends in molecular modelling are geared towards increasingly realistic representations of the modelled systems. This is reflected in larger, more complex systems, which are difficult to build and would ideally rely on a software that converts userprovided descriptors into system coordinates. This is not a trivial task, as the building algorithms use simplifications that can introduce inaccuracies in the system properties that do not correspond to the requested values. We created COBY, a coarse-grained system builder that can create a large variety of systems in a single command call using Martini molecule models. We improved the accuracy of the complex membrane and solvent building procedures, introduced a variety of arguments that can be used to build diverse systems, and implemented features intended for force field development. COBY can be used to build flat membranes of any degree of complexity, handle protein and solvent insertion, solute flooding, stacked membranes, membrane patches and pores, and includes advanced functionalities such as molecule import, lipid building from fragments, handling of multiple parameter libraries, and several choices of algorithms for interpreting user-provided system descriptors. COBY is an open-source software written in Python 3, and the code, documentation, and tutorials are hosted at github.com/MikkelDA/COBY. TOC Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/604601v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@15e46a4org.highwire.dtl.DTLVardef@6fd668org.highwire.dtl.DTLVardef@657541org.highwire.dtl.DTLVardef@f51840_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2022

A pH-dependent cluster of charges in a conserved cryptic pocket on flaviviral envelopes

Flaviviruses are enveloped viruses which include numerous human pathogens of escalating global health concern that are predominantly transmitted by mosquitoes and ticks. Some, such as dengue virus, exhibit the phenomenon of antibody-dependent enhancement (ADE) of disease, making traditional vaccine-based routes of fighting viral infections problematic. The pH-dependent conformational change of the envelope (E) protein required for fusion between the viral and endosomal membranes is an attractive point of inhibition by antivirals as it also has the potential to diminish the effects of ADE. Here, we systematically examined six flaviviruses by employing large-scale molecular dynamics (MD) simulations of a [~]400,000 atom raft system that represents a substantial portion of the curved flaviviral envelope. We utilised a benzene-mapping approach over a total of 14 s of sampling time, leading to discovery of shared hotspots and elucidation of the dynamic behaviour of conserved cryptic sites. A cryptic pocket previously shown to bind a detergent molecule exhibited significant strain-specific characteristics. An alternative conserved cryptic site located at the E protein domain interfaces showed a more consistent dynamic behaviour across flaviviruses and contains a buried, conserved cluster of ionisable residues that includes His144, previously implicated in the pH-dependent conformational switch required for fusion. The dynamics of the cluster were further explored in extensive constant-pH simulations and revealed cluster and domain-interface disruption under low pH conditions. Based on this, we propose a cluster-dependent mechanism that addresses inconsistencies in the histidine-switch hypothesis and highlights the role of cluster protonation in orchestrating the domain dissociation pivotal for the formation of the fusogenic trimer. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/499710v1_ufig1.gif" ALT="Figure 1"> View larger version (58K): org.highwire.dtl.DTLVardef@2a90feorg.highwire.dtl.DTLVardef@9535a1org.highwire.dtl.DTLVardef@1f41ae0org.highwire.dtl.DTLVardef@1106e41_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2021

Uncovering cryptic pockets in the SARS-CoV-2 spike glycoprotein

The recent global COVID-19 pandemic has prompted a rapid response in terms of vaccine and drug development targeting the viral pathogen, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this work, we modelled a complete membrane-embedded SARS-CoV-2 spike (S) protein, the primary target of vaccine and therapeutics development, based on available structural data and known glycan content. We then used molecular dynamics (MD) simulations to study the system in the presence of benzene probes designed to enhance discovery of cryptic, potentially druggable pockets on the S protein surface. We uncovered a novel cryptic pocket with promising druggable properties located underneath the 617-628 loop, which was shown to be involved in the formation of S protein multimers on the viral surface. A marked multi-conformational behaviour of this loop in simulations was validated using hydrogen-deuterium exchange mass spectrometry (HDX-MS) experiments, supportive of opening and closing dynamics. Interestingly, the pocket is also the site of the D614G mutation, known to be important for SARS-CoV-2 fitness, and within close proximity to mutations in the novel SARS-CoV-2 strains B.1.1.7 and B.1.1.28, both of which are associated with increased transmissibility and severity of infection. The pocket was present in systems emulating both immature and mature glycosylation states, suggesting its druggability may not be dependent upon the stage of virus maturation. Overall, the predominantly hydrophobic nature of the cryptic pocket, its well conserved surface, and proximity to regions of functional relevance in viral assembly and fitness are all promising indicators of its potential for therapeutic targeting. Our method also successfully recapitulated hydrophobic pockets in the receptor binding domain and N-terminal domain associated with detergent or lipid binding in prior cryo-electron microscopy (cryo-EM) studies. Collectively, this work highlights the utility of the benzene mapping approach in uncovering potential druggable sites on the surface of SARS-CoV-2 targets.

biophysics↗

bioRxiv2021

Site-specific steric control of SARS-CoV-2 spike glycosylation

A central tenet in the design of vaccines is the display of native-like antigens in the elicitation of protective immunity. The abundance of N-linked glycans across the SARS-CoV-2 spike protein is a potential source of heterogeneity between the many different vaccine candidates under investigation. Here, we investigate the glycosylation of recombinant SARS-CoV-2 spike proteins from five different laboratories and compare them against infectious virus S protein. We find patterns which are conserved across all samples and this can be associated with site-specific stalling of glycan maturation which act as a highly sensitive reporter of protein structure. Molecular dynamics (MD) simulations of a fully glycosylated spike support s a model of steric restrictions that shape enzymatic processing of the glycans. These results suggest that recombinant spike-based SARS-CoV-2 immunogen glycosylation reproducibly recapitulates signatures of viral glycosylation.

biochemistry↗

bioRxiv2020

A benzene-mapping approach for uncovering cryptic pockets in membrane-bound proteins

Molecular dynamics (MD) simulations in combination with small organic probes present in the solvent have previously been used as a method to reveal cryptic pockets that may not have been identified in experimental structures. We report such a method implemented within the CHARMM forcefield to effectively explore cryptic pockets on the surfaces of membrane-embedded proteins using benzene as a probe molecule. This relies on modified non-bonded parameters in addition to repulsive potentials between membrane lipids and benzene molecules. The method was tested on part of the outer shell of the dengue virus (DENV), for which research into a safe and effective neutralizing antibody or drug molecule is still ongoing. In particular, the envelope (E) protein, associated with the membrane (M) protein, is a lipid membrane-embedded complex which forms a dimer in the mature viral envelope. Solvent mapping was performed for the full, membrane-embedded EM protein complex and compared with similar calculations performed for the isolated, soluble E protein ectodomain dimer in solvent. Ectodomain-only simulations with benzene exhibited unfolding effects not observed in the more physiologically relevant membrane-associated systems. A cryptic pocket which has been experimentally shown to bind n-octyl-{beta}-D-glucoside detergent was consistently revealed in all benzene-containing simulations. The addition of benzene also enhanced the flexibility and hydrophobic exposure of cryptic pockets at a key, functional interface in the E protein, and revealed a novel, potentially druggable pocket that may be targeted to prevent conformational changes associated with viral entry into the cell. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=131 SRC="FIGDIR/small/025163v1_ufig1.gif" ALT="Figure 1"> View larger version (73K): org.highwire.dtl.DTLVardef@abe537org.highwire.dtl.DTLVardef@155a741org.highwire.dtl.DTLVardef@57bff6org.highwire.dtl.DTLVardef@fbee3a_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗