scholarly journals D614G substitution at the hinge region enhances the stability of trimeric SARS-CoV-2 spike protein

2021 ◽  
Vol 17 (3) ◽  
pp. 439-445
Author(s):  
Arangasamy Yazhini ◽  
◽  
◽  
Keyword(s):  
Free Energy ◽  
Thermodynamic Stability ◽  
Normal Mode Analysis ◽  
Protein Structures ◽  
Energy Difference ◽  
Hinge Region ◽  
Spike Protein ◽  
Mode Analysis ◽  
The Stability ◽  
Domain Motions

Mutations in the spike protein of SARS-CoV-2 are the major causes for the modulation of ongoing COVID-19 infection. Currently, the D614G substitution in the spike protein has become dominant worldwide. It is associated with higher infectivity than the ancestral (D614) variant. We demonstrate using Gaussian network model-based normal mode analysis that the D614G substitution occurs at the hinge region that facilitates domain-domain motions between receptor binding domain and S2 region of the spike protein. Computer-aided mutagenesis and inter-residue energy calculations reveal that contacts involving D614 are energetically frustrated. However, contacts involving G614 are energetically favourable, implying the substitution strengthens residue contacts that are formed within as well as between protomers. We also find that the free energy difference (ΔΔG) between two variants is -2.6 kcal/mol for closed and -2.0 kcal/mol for 1-RBD up conformation. Thus, the hermodynamic stability has increased upon D614G substitution. Whereas the reverse mutation in spike protein structures having G614 substitution has resulted in the free energy differences of 6.6 kcal/mol and 6.3 kcal/mol for closed and 1-RBD up conformations, respectively, indicating that the overall thermodynamic stability has decreased. These results suggest that the D614G substitution modulates the flexibility of spike protein and confers enhanced thermodynamic stability irrespective of conformational states. This data concurs with the known information demonstrating increased availability of the functional form of spike protein trimer upon D614G substitution.

scholarly journals D614G substitution at the hinge region enhances the stability of trimeric SARS-CoV-2 spike protein

2021 ◽  
Author(s):  
Arangasamy Yazhini ◽  
Das Swayam Prakash Sidhanta ◽  
Narayanaswamy Sriniva
Keyword(s):  
Free Energy ◽  
Thermodynamic Stability ◽  
Normal Mode Analysis ◽  
Protein Flexibility ◽  
Energy Difference ◽  
Hinge Region ◽  
Spike Protein ◽  
Mode Analysis ◽  
Free Energy Difference ◽  
Residue Interaction

Abstract Background Spike protein is a key player in the SARS-CoV-2 infection by mediating primary contact between the virus and host cell surface. In the current COVID-19 pandemic, a variant of SARS-CoV-2 having D614G substitution in the spike protein has become dominant world-wide. Initial characterization of the virus shows that the G614 variant is more infectious and has higher fitness than the ancestral (D614) variant. In this study, we analyzed the significance of the D614G substitution on the protein flexibility, inter-residue interaction energies and thermostability of the spike protein trimer. Results Using Gaussian network model-based normal mode analysis, we demonstrate that D614G substitution occurs at hinge region that facilitates domain-domain motions between receptor binding domain and S2 region of the spike protein. Further, in-silico mutagenesis and inter-residue energy calculations reveal that contacts involving D614 are energetically frustrated whereas contacts involving G614 are energetically favourable implying the substitution strengthens intra- as well as inter-protomers association. Upon glycine substitution, free energy difference (ΔΔG) is -2.6 kcal/mol for closed and − 2.0 kcal/mol for 1-RBD up conformation i.e., thermodynamic stability has increased. When we perform reverse mutation in the structures of spike protein having G614 substitution, we observe that the free energy difference is 6.6 kcal/mol and 6.3 kcal/mol for closed and 1-RBD up conformations respectively indicating lowered thermodynamic stability. Together, these observations suggest that D614G substitution could modulate the flexibility of spike protein and confer enhanced thermodynamic stability. Conclusion Our results on protein flexibility and energetic basis of enhanced stability hint that G614 likely increases the availability of functional form of spike trimer thereby associated to increased infectivity.

scholarly journals D614G substitution enhances the stability of trimeric SARS-CoV-2 spike protein

2020 ◽  
Author(s):  
Arangasamy Yazhini ◽  
Das Swayam Prakash Sidhanta ◽  
Narayanaswamy Srinivasan
Keyword(s):  
Thermodynamic Stability ◽  
Energy Difference ◽  
Spike Protein ◽  
Interaction Energies ◽  
Free Energy Difference ◽  
Residue Interaction ◽  
Ancestral Virus ◽  
Glycine Substitution ◽  
Favourable Environment ◽  
The Stability

AbstractSARS-CoV-2 spike protein with D614G substitution has become the dominant variant in the ongoing COVID-19 pandemic. Several studies to characterize the new virus expressing G614 variant show that it exhibits increased infectivity compared to the ancestral virus having D614 spike protein. Here, using in-silico mutagenesis and energy calculations, we analyzed inter-residue interaction energies and thermodynamic stability of the dominant (G614) and the ancestral (D614) variants of spike protein trimer in ‘closed’ and ‘partially open’ conformations. We find that the local interactions mediated by aspartate at the 614th position are energetically frustrated and create unfavourable environment. Whereas, glycine at the same position confers energetically favourable environment and strengthens intra-as well as inter-protomer association. Such changes in the local interaction energies enhance the thermodynamic stability of the spike protein trimer as free energy difference (ΔΔG) upon glycine substitution is −2.6 kcal/mol for closed conformation and −2.0 kcal/mol for open conformation. Our results on the structural and energetic basis of enhanced stability hint that G614 may confer increased availability of functional form of spike protein trimer and consequent in higher infectivity than the D614 variant.

scholarly journals An Effective MM/GBSA Protocol for Absolute Binding Free Energy Calculations: A Case Study on SARS-CoV-2 Spike Protein and the Human ACE2 Receptor

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2383
Author(s):  
Negin Forouzesh ◽  
Nikita Mishra
Keyword(s):  
Free Energy ◽  
Binding Free Energy ◽  
Normal Mode Analysis ◽  
Free Energy Calculations ◽  
Spike Protein ◽  
Upper And Lower Bounds ◽  
Mode Analysis ◽  
Implicit Solvent ◽  
Energy Calculation ◽  
Generalized Born

The binding free energy calculation of protein–ligand complexes is necessary for research into virus–host interactions and the relevant applications in drug discovery. However, many current computational methods of such calculations are either inefficient or inaccurate in practice. Utilizing implicit solvent models in the molecular mechanics generalized Born surface area (MM/GBSA) framework allows for efficient calculations without significant loss of accuracy. Here, GBNSR6, a new flavor of the generalized Born model, is employed in the MM/GBSA framework for measuring the binding affinity between SARS-CoV-2 spike protein and the human ACE2 receptor. A computational protocol is developed based on the widely studied Ras–Raf complex, which has similar binding free energy to SARS-CoV-2/ACE2. Two options for representing the dielectric boundary of the complexes are evaluated: one based on the standard Bondi radii and the other based on a newly developed set of atomic radii (OPT1), optimized specifically for protein–ligand binding. Predictions based on the two radii sets provide upper and lower bounds on the experimental references: −14.7(ΔGbindBondi)<−10.6(ΔGbindExp.)<−4.1(ΔGbindOPT1) kcal/mol. The consensus estimates of the two bounds show quantitative agreement with the experiment values. This work also presents a novel truncation method and computational strategies for efficient entropy calculations with normal mode analysis. Interestingly, it is observed that a significant decrease in the number of snapshots does not affect the accuracy of entropy calculation, while it does lower computation time appreciably. The proposed MM/GBSA protocol can be used to study the binding mechanism of new variants of SARS-CoV-2, as well as other relevant structures.

Application of the ESMACS Binding Free Energy Protocol to a Highly Varied Ligand Dataset: Lactate Dehydogenase A

2019 ◽  
Author(s):  
David Wright ◽  
Fouad Husseini ◽  
Shunzhou Wan ◽  
Christophe Meyer ◽  
Herman Van Vlijmen ◽  
...  
Keyword(s):  
Free Energy ◽  
Surface Area ◽  
Binding Free Energy ◽  
Normal Mode Analysis ◽  
Binding Mode ◽  
Accessible Surface Area ◽  
Solvent Accessible Surface Area ◽  
Mode Analysis ◽  
Energy Calculation ◽  
Accessible Surface

<div>Here, we evaluate the performance of our range of ensemble simulation based binding free energy calculation protocols, called ESMACS (enhanced sampling of molecular dynamics with approximation of continuum solvent) for use in fragment based drug design scenarios. ESMACS is designed to generate reproducible binding affinity predictions from the widely used molecular mechanics Poisson-Boltzmann surface area (MMPBSA) approach. We study ligands designed to target two binding pockets in the lactate dehydogenase A target protein, which vary in size, charge and binding mode. When comparing to experimental results, we obtain excellent statistical rankings across this highly diverse set of ligands. In addition, we investigate three approaches to account for entropic contributions not captured by standard MMPBSA calculations: (1) normal mode analysis, (2) weighted solvent accessible surface area (WSAS) and (3) variational entropy. </div>

scholarly journals Unraveling the stability landscape of mutations in the SARS-CoV-2 receptor-binding domain

2020 ◽  
Author(s):  
Mohamed Raef Smaoui ◽  
Hamdi Yahyaoui
Keyword(s):  
Receptor Binding ◽  
Single Point ◽  
Protein Structures ◽  
Point Mutations ◽  
Binding Domain ◽  
Spike Protein ◽  
Receptor Binding Domain ◽  
Point Mutant ◽  
The Stability ◽  
Spike Proteins

Abstract The interaction between the receptor-binding domain of the SARS-CoV-2 spike glycoprotein and the ACE2 enzyme is believed to be the entry point of the virus into various cells in the body, including the lungs, heart, liver, and kidneys. The current focus of several therapeutic design efforts explore attempts at affecting the binding interaction between the two proteins to limit the activity of the virus and disease progression. In this work, we analyze the stability of the spike protein under all possible single-point mutations in the receptor-binding domain and computationally explore mutations that can affect the binding with the ACE2 enzyme. We unravel the mutation landscape of the receptor region and assess the toxicity potential of single and multi-point mutations, generating insights for future vaccine efforts on potential mutations that might further stabilize the spike protein and increase its infectivity. We developed a tool, called SpikeMutator, to construct full atomic protein structures of the mutant spike proteins and shared a database of 3,800 single-point mutant structures. We analyzed the recent 65,000 reported spike sequences across the globe and observed the emergence of stable multi-point mutant structures. Using the landscape, we searched through 7.5 million possible 2-point mutation combinations and report that the (R355D K424E) mutation produces one of the strongest spike proteins that therapeutic efforts should investigate for the sake of developing an effective vaccine.

scholarly journals Thermosolutal Instability in Compressible Viscoelastic Dusty Fluid through Porous Medium

2013 ◽  
Vol 18 (1) ◽  
pp. 99-112 ◽  
Author(s):  
P. Kumar ◽  
H. Mohan
Keyword(s):  
Porous Medium ◽  
Viscoelastic Fluid ◽  
Normal Mode Analysis ◽  
Suspended Particles ◽  
Mode Analysis ◽  
Stationary Convection ◽  
Linearized Stability ◽  
Medium Permeability ◽  
The Stability ◽  
Solute Gradient

Thermosolutal instability in a compressible Walters B’ viscoelastic fluid with suspended particles through a porous medium is considered. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For stationary convection, the Walters B’ viscoelastic fluid behaves like a Newtonian fluid and it is found that suspended particles and medium permeability have a destabilizing effect whereas the stable solute gradient and compressibility have a stabilizing effect on the system. Graphs have been plotted by giving numerical values to the parameters to depict the stability characteristics. The stable solute gradient and viscoelasticity are found to introduce oscillatory modes in the system which are non-existent in their absence.

scholarly journals ProSNEx: a web-based application for exploration and analysis of protein structures using network formalism

2019 ◽  
Vol 47 (W1) ◽  
pp. W471-W476 ◽  
Author(s):  
Rasim Murat Aydınkal ◽  
Onur Serçinoğlu ◽  
Pemra Ozbek
Keyword(s):  
Protein Structure ◽  
Normal Mode Analysis ◽  
Shortest Paths ◽  
Protein Structures ◽  
Interaction Strength ◽  
Biological Information ◽  
Coarse Grained ◽  
Mode Analysis ◽  
Residue Interaction ◽  
Natural Variant

AbstractProSNEx (Protein Structure Network Explorer) is a web service for construction and analysis of Protein Structure Networks (PSNs) alongside amino acid flexibility, sequence conservation and annotation features. ProSNEx constructs a PSN by adding nodes to represent residues and edges between these nodes using user-specified interaction distance cutoffs for either carbon-alpha, carbon-beta or atom-pair contact networks. Different types of weighted networks can also be constructed by using either (i) the residue-residue interaction energies in the format returned by gRINN, resulting in a Protein Energy Network (PEN); (ii) the dynamical cross correlations from a coarse-grained Normal Mode Analysis (NMA) of the protein structure; (iii) interaction strength. Upon construction of the network, common network metrics (such as node centralities) as well as shortest paths between nodes and k-cliques are calculated. Moreover, additional features of each residue in the form of conservation scores and mutation/natural variant information are included in the analysis. By this way, tool offers an enhanced and direct comparison of network-based residue metrics with other types of biological information. ProSNEx is free and open to all users without login requirement at http://prosnex-tool.com.

Linearized theory of inhomogeneous multiple ‘water-bag’ plasmas

1973 ◽  
Vol 9 (2) ◽  
pp. 235-247 ◽  
Author(s):  
H. W. Bloomberg ◽  
H. L. Berk
Keyword(s):  
Boundary Conditions ◽  
Normal Mode ◽  
Normal Mode Analysis ◽  
Mode Analysis ◽  
Special Boundary ◽  
Finite Region ◽  
Trapped Particles ◽  
Linearized Theory ◽  
Beam Approximation ◽  
The Stability

The problem of the stability of inhomogeneous, electrostatic, multiple water-bag plasmas is considered. Equations are derived for general stationary water-bag equilibria, as well as for the corresponding perturbations. Particular attention is directed to systems with trapped particles in periodic equilibria, and special boundary conditions for the perturbation equations at the trapped-particle turning points are introduced. A normal-mode analysis is carried out for a configuration involving trapped particles occupying a finite region in the vicinity of the trough of an equilibrium wave (BGK mode). The results confirm the validity of the bunched-beam approximation.

scholarly journals Energy Landscape of the SARS-CoV-2 Reveals Extensive Conformational Heterogeneity

2021 ◽  
Author(s):  
Ghoncheh Mashayekhi ◽  
John Vant ◽  
Abhishek Singharoy ◽  
Abbas Ourmazd
Keyword(s):  
Free Energy ◽  
Energy Landscape ◽  
Binding Pocket ◽  
Minimum Free Energy ◽  
Spike Protein ◽  
Local Analysis ◽  
Interaction Sites ◽  
Density Maps ◽  
The Stability ◽  
Global And Local

Cryo-electron microscopy (cryo-EM) has produced a number of structural models of the SARS-CoV-2 spike, already prompting biomedical outcomes. However, these reported models and their associated electrostatic potential maps represent an unknown admixture of conformations stemming from the underlying energy landscape of the spike protein. As for any protein, some of the spike's conformational motions are expected to be biophysically relevant, but cannot be interpreted only by static models. Using experimental cryo-EM images, we present the energy landscape of the spike protein conformations, and identify molecular rearrangements along the most-likely conformational path in the vicinity of the open (so called 1RBD-up) state. The resulting global and local atomic refinements reveal larger movements than those expected by comparing the reported 1RBD-up and 1RBD-down cryo-EM models. Here we report greater degrees of "openness" in global conformations of the 1RBD-up state, not revealed in the single-model interpretations of the density maps, together with conformations that overlap with the reported models. We discover how the glycan shield contributes to the stability of these conformations along the minimum free-energy pathway. A local analysis of seven key binding pockets reveals that six out them, including those for engaging ACE2, therapeutic mini-proteins, linoleic acid, two different kinds of antibodies, and protein-glycan interaction sites, switch conformations between their known apo- and holo-conformations, even when the global spike conformation is 1RBD-up. This is reminiscent of a conformational pre-equilibrium. We found only one binding pocket, namely antibody AB-C135 to remain closed along the entire minimum free energy path, suggesting an induced fit mechanism for this enzyme.

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