scholarly journals Structural Analysis Of The Receptor Binding Motif Of Spike Glycoprotein Explains The High Stability Of SARS-CoV-2 RBD/hACE2-complex

2020 ◽  
Author(s):  
Akshay Nileshkumar Pandya
Keyword(s):  
Structural Analysis ◽  
Host Cell ◽  
Receptor Binding ◽  
Structural Changes ◽  
Host Cells ◽  
Binding Motif ◽  
Spike Glycoprotein ◽  
Furin Cleavage ◽  
Furin Cleavage Site ◽  
The Stability

SARS-CoV and SARS-CoV-2 both are the Coronaviruses causing Severe Acute Respiratory Syndrome(SARS). Genomes of both SARS-viruses are identical and they both use Spike glycoprotein to enter the host cell. hACE2(human Angiotensin-Converting Enzyme) is the receptor used by both viruses to enter the host cell. Despite the similar structures, the SARS-CoV-2 is more infective compared to the SARS-CoV. As the SARS-CoV-2 RBD/hACE2 complex is more stable compared to the SARS-CoV RBD/hACE2 complex, the SARS-CoV-2 is more effective in terms of entering the host cells. Structural analysis revealed that the addition of a Furin cleavage site and the structural changes in Receptor Binding Domain(RBD) of the Spike protein are mainly responsible for this increase in the stability. Differences between the structure of the Spike glycoproteins of SARS-CoV and SARS-CoV-2 are discussed in-depth and an attempt to correlate them with increased infectivity of the SARS-CoV-2(compared to the SARS-CoV) is made.

scholarly journals SARS-CoV-2 convergent evolution as a guide to explore adaptive advantage

2021 ◽  
Author(s):  
Jiri Zahradnik ◽  
Jaroslav Nunvar ◽  
Gideon Schreiber
Keyword(s):  
Receptor Binding ◽  
Convergent Evolution ◽  
Great Majority ◽  
Viral Population ◽  
Binding Motif ◽  
Furin Cleavage ◽  
S Protein ◽  
Adaptive Mutations ◽  
Furin Cleavage Site ◽  
Protein Receptor

Much can be learned from 1.2 million sequences of SARS-CoV-2 generated during the last 15 months. Out of the overwhelming number of mutations sampled so far, only few rose to prominence in the viral population. Many of these emerged recently and independently in multiple lineages. Such a textbook example of convergent evolution at the molecular level is not only curiosity but a guide to uncover the basis for adaptive advantage behind these events. Focusing on the extent of the convergent evolution in the spike (S) protein, our report confirms that the most concerning SARS-CoV-2 lineages carry the heaviest burden of convergent S-protein mutations, suggesting their fundamental adaptive advantage. The great majority (21/25) of S-protein sites under convergent evolution tightly cluster in three functional domains; N-terminal domain, receptor-binding domain, and Furin cleavage site. We further show that among the S-protein receptor-binding motif mutations, ACE2 affinity-improving substitutions are favored. While the probed mutation space in the S protein covered all amino-acids reachable by single nucleotide changes, substitutions requiring two nucleotide changes or epistatic mutations of multiple-residues have only recently started to emerge. Unfortunately, despite their convergent emergence and physical association, most of these adaptive mutations and their combinations remain understudied. We aim to promote research of current variants which are currently understudied but may become important in the future.

scholarly journals Spike glycoprotein and host cell determinants of SARS-CoV-2 entry and cytopathic effects

2020 ◽  
Author(s):  
Hanh T. Nguyen ◽  
Shijian Zhang ◽  
Qian Wang ◽  
Saumya Anang ◽  
Jia Wang ◽  
...  
Keyword(s):  
Host Cell ◽  
Cell Fusion ◽  
Cleavage Site ◽  
Virus Entry ◽  
Cytoplasmic Tail ◽  
Syncytium Formation ◽  
Spike Glycoprotein ◽  
Furin Cleavage ◽  
Cytopathic Effects ◽  
Furin Cleavage Site

SARS-CoV-2, a betacoronavirus, is the cause of the COVID-19 pandemic. The SARS-CoV-2 spike (S) glycoprotein trimer mediates virus entry into host cells and cytopathic effects (syncytium formation). We studied the contribution of several S glycoprotein features to these functions, focusing on those that differ among related coronaviruses. Acquisition of the furin cleavage site by the SARS-CoV-2 S glycoprotein decreased virus stability and infectivity, but greatly enhanced syncytium-forming ability. Notably, the D614G change found in globally predominant SARS-CoV-2 strains increased infectivity, modestly enhanced responsiveness to the ACE2 receptor and susceptibility to neutralizing sera, and tightened association of the S1 subunit with the trimer. Apparently, these two features of the SARS-CoV-2 S glycoprotein, the furin cleavage site and D614G, have evolved to balance virus infectivity, stability, cytopathicity and antibody vulnerability. Although the endodomain (cytoplasmic tail) of the S2 subunit was not absolutely required for virus entry or syncytium formation, alteration of palmitoylated cysteine residues in the cytoplasmic tail decreased the efficiency of these processes. As proteolytic cleavage contributes to the activation of the SARS-CoV-2 S glycoprotein, we evaluated the ability of protease inhibitors to suppress S glycoprotein function. Matrix metalloprotease inhibitors suppressed S-mediated cell-cell fusion, but not virus entry. Synergy between inhibitors of matrix metalloproteases and TMPRSS2 suggests that both host proteases can activate the S glycoprotein during the process of syncytium formation. These results provide insights into SARS-CoV-2 S glycoprotein-host cell interactions that likely contribute to the transmission and pathogenicity of this pandemic agent. IMPORTANCE The development of an effective and durable SARS-CoV-2 vaccine is essential for combating the growing COVID-19 pandemic. The SARS-CoV-2 spike (S) glycoprotein is the main target of neutralizing antibodies elicited during virus infection or following vaccination. Knowledge of the spike glycoprotein evolution, function and interactions with host factors will help researchers to develop effective vaccine immunogens and treatments. Here we identify key features of the spike glycoprotein, including the furin cleavage site and the D614G natural mutation, that modulate viral cytopathic effects, infectivity and sensitivity to inhibition. We also identify two inhibitors of host metalloproteases that block S-mediated cell-cell fusion, a process that contributes to the destruction of the virus-infected cell.

Spike glycoprotein and host cell determinants of SARS-CoV-2 entry and cytopathic effects

2020 ◽  
Author(s):  
Hanh T. Nguyen ◽  
Shijian Zhang ◽  
Qian Wang ◽  
Saumya Anang ◽  
Jia Wang ◽  
...  
Keyword(s):  
Host Cell ◽  
Cell Fusion ◽  
Cleavage Site ◽  
Virus Entry ◽  
Cytoplasmic Tail ◽  
Syncytium Formation ◽  
Spike Glycoprotein ◽  
Furin Cleavage ◽  
Cytopathic Effects ◽  
Furin Cleavage Site

ABSTRACTSARS-CoV-2, a betacoronavirus, is the cause of the COVID-19 pandemic. The SARS-CoV-2 spike (S) glycoprotein trimer mediates virus entry into host cells and cytopathic effects. We studied the contribution of several S glycoprotein features to these functions, focusing on those that differ among related coronaviruses. Acquisition of the furin cleavage site by the SARS-CoV-2 S glycoprotein decreased virus stability and infectivity, but greatly enhanced the ability to form lethal syncytia. Notably, the D614G change found in globally predominant SARS-CoV-2 strains restored infectivity, modestly enhanced responsiveness to the ACE2 receptor and susceptibility to neutralizing sera, and tightened association of the S1 subunit with the trimer. Apparently, two unique features of the SARS-CoV-2 S glycoprotein, the furin cleavage site and D614G, have evolved to balance virus infectivity, stability, cytopathicity and antibody vulnerability. Although the endodomain (cytoplasmic tail) of the S2 subunit was not absolutely required for virus entry or syncytium formation, alteration of palmitoylated cysteine residues in the cytoplasmic tail decreased the efficiency of these processes. As proteolytic cleavage contributes to the activation of the SARS-CoV-2 S glycoprotein, we evaluated the ability of protease inhibitors to suppress S glycoprotein function. Matrix metalloprotease inhibitors suppressed S-mediated cell-cell fusion, but not virus entry. Synergy between inhibitors of matrix metalloproteases and TMPRSS2 suggests that both proteases can activate the S glycoprotein during the process of syncytium formation. These results provide insights into SARS-CoV-2 S glycoprotein-host cell interactions that likely contribute to the transmission and pathogenicity of this pandemic agent.IMPORTANCEThe development of an effective and durable SARS-CoV-2 vaccine is essential for combating the growing COVID-19 pandemic. The SARS-CoV-2 spike (S) glycoprotein is the main target of neutralizing antibodies elicited during virus infection or following vaccination. Knowledge of the spike glycoprotein evolution, function and interactions with host factors will help researchers to develop effective vaccine immunogens and treatments. Here we identify key features of the spike glycoprotein, including the furin cleavage site and the D614G natural mutation, that modulate viral cytopathic effects, infectivity and sensitivity to inhibition. We also identify two inhibitors of host metalloproteases that block S-mediated cell-cell fusion, which contributes to the destruction of the virus-infected cell.

scholarly journals Investigation of Critical Binding Pattern in SARS-CoV-2 Spike Glycoprotein with Angiotensin-Converting Enzyme 2: An in Silico Analysis 

2020 ◽  
Author(s):  
Farzaneh Jafary ◽  
Sepideh Jafari ◽  
Mohamad Reza Ganjalikhany
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Host Cell ◽  
Receptor Binding ◽  
In Silico ◽  
Lung Epithelial Cells ◽  
Binding Motif ◽  
Converting Enzyme ◽  
Spike Glycoprotein ◽  
Angiotensin Converting Enzyme 2 ◽  
Free Energy Decomposition

Abstract Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a newly-discovered coronavirus and responsible for the spread of coronavirus disease 2019 (COVID-19). SARS-CoV-2 infected millions of people in the world and immediately became a pandemic in March 2020. SARS-CoV-2 belongs to the beta-coronavirus genus of the large family of Coronaviridae. It is now known that its surface spike glycoprotein binds to the angiotensin-converting enzyme-2 (ACE2), which is expressed on the lung epithelial cells, mediates the fusion of the cellular and viral membranes, and facilitates the entry of viral genome to the host cell. Therefore, blocking the virus-cell interaction could be a potential target for the prevention of viral infection. The binding of SARS-CoV-2 to ACE2 is a protein-protein interaction, and so, analyzing the structure of the spike glycoprotein of SARS-CoV-2 and its underlying mechanism to bind the host cell receptor would be useful for the management and treatment of COVID-19. In this study, we performed comparative in silico studies to deeply understand the structural and functional details of the interaction between the spike glycoprotein of SARS-CoV-2 and its cognate cellular receptor ACE2. According to our results, the affinity of the ACE2 receptor for SARS-CoV-2 was higher than SARS-CoV. According to the free energy decomposition of the spike glycoprotein-ACE2 complex, we found critical points in three areas which are responsible for the increased binding affinity of SARS-CoV-2 compared with SARS-CoV. These mutations occurred at the receptor-binding domain of the spike glycoprotein that play an essential role in the increasing the affinity of coronavirus to ACE2. For instance, mutations Pro462Ala and Leu472Phe resulted in the altered binding energy from -2 kcal·mol−1 in SARS-COV to -6 kcal·mol−1 in SARS-COV-2. The results demonstrated that some mutations in the receptor-binding motif could be considered as a hot-point for designing potential drugs to inhibit the interaction between the spike glycoprotein and ACE2.

Is the Rigidity of SARS-CoV-2 Spike Receptor-Binding Motif the Hallmark for Its Enhanced Infectivity and Pathogenesis?

2020 ◽  
Author(s):  
Angelo Spinello ◽  
Andrea Saltalamacchia ◽  
Alessandra Magistrato
Keyword(s):  
Health Economic ◽  
Global Health ◽  
Receptor Binding ◽  
Binding Motif ◽  
Spike Glycoprotein ◽  
High Affinity ◽  
Global Pandemic ◽  
Medical Countermeasures ◽  
High Infectivity ◽  
Human Receptor

<p>The latest outbreak of a new pathogenic coronavirus (SARS-CoV-2) is provoking a global health, economic and societal crisis. All-atom simulations enabled us to uncover the key molecular traits underlying the high affinity of SARS-CoV-2 spike glycoprotein towards its human receptor, providing a rationale to its high infectivity. Harnessing this knowledge can boost developing effective medical countermeasures to fight the current global pandemic.</p>

scholarly journals A Fungal Defensin Targets the SARS−CoV−2 Spike Receptor−Binding Domain

2021 ◽  
Vol 7 (7) ◽  
pp. 553
Author(s):  
Bin Gao ◽  
Shunyi Zhu
Keyword(s):  
Receptor Binding ◽  
Viral Entry ◽  
Single Point ◽  
Binding Domain ◽  
Host Cells ◽  
Single Point Mutation ◽  
Binding Motif ◽  
Microsporum Canis ◽  
Receptor Binding Domain ◽  
Fungal Defensin

Coronavirus Disease 2019 (COVID−19) elicited by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS−CoV−2) is calling for novel targeted drugs. Since the viral entry into host cells depends on specific interactions between the receptor−binding domain (RBD) of the viral Spike protein and the membrane−bound monocarboxypeptidase angiotensin converting enzyme 2 (ACE2), the development of high affinity RBD binders to compete with human ACE2 represents a promising strategy for the design of therapeutics to prevent viral entry. Here, we report the discovery of such a binder and its improvement via a combination of computational and experimental approaches. The binder micasin, a known fungal defensin from the dermatophytic fungus Microsporum canis with antibacterial activity, can dock to the crevice formed by the receptor−binding motif (RBM) of RBD via an extensive shape complementarity interface (855.9 Å2 in area) with numerous hydrophobic and hydrogen−bonding interactions. Using microscale thermophoresis (MST) technique, we confirmed that micasin and its C−terminal γ−core derivative with multiple predicted interacting residues exhibited a low micromolar affinity to RBD. Expanding the interface area of micasin through a single point mutation to 970.5 Å2 accompanying an enhanced hydrogen bond network significantly improved its binding affinity by six−fold. Our work highlights the naturally occurring fungal defensins as an emerging resource that may be suitable for the development into antiviral agents for COVID−19.

scholarly journals The Functional Consequences of the Novel Ribosomal Pausing Site in SARS-CoV-2 Spike Glycoprotein RNA

2021 ◽  
Vol 22 (12) ◽  
pp. 6490
Author(s):  
Olga A. Postnikova ◽  
Sheetal Uppal ◽  
Weiliang Huang ◽  
Maureen A. Kane ◽  
Rafael Villasmil ◽  
...  
Keyword(s):  
Amino Acid ◽  
Insertion Sequence ◽  
Experimental Studies ◽  
Spike Protein ◽  
Spike Glycoprotein ◽  
Furin Cleavage ◽  
New Host ◽  
S Protein ◽  
Furin Cleavage Site ◽  
Ribosome Pausing

The SARS-CoV-2 Spike glycoprotein (S protein) acquired a unique new 4 amino acid -PRRA- insertion sequence at amino acid residues (aa) 681–684 that forms a new furin cleavage site in S protein as well as several new glycosylation sites. We studied various statistical properties of the -PRRA- insertion at the RNA level (CCUCGGCGGGCA). The nucleotide composition and codon usage of this sequence are different from the rest of the SARS-CoV-2 genome. One of such features is two tandem CGG codons, although the CGG codon is the rarest codon in the SARS-CoV-2 genome. This suggests that the insertion sequence could cause ribosome pausing as the result of these rare codons. Due to population variants, the Nextstrain divergence measure of the CCU codon is extremely large. We cannot exclude that this divergence might affect host immune responses/effectiveness of SARS-CoV-2 vaccines, possibilities awaiting further investigation. Our experimental studies show that the expression level of original RNA sequence “wildtype” spike protein is much lower than for codon-optimized spike protein in all studied cell lines. Interestingly, the original spike sequence produces a higher titer of pseudoviral particles and a higher level of infection. Further mutagenesis experiments suggest that this dual-effect insert, comprised of a combination of overlapping translation pausing and furin sites, has allowed SARS-CoV-2 to infect its new host (human) more readily. This underlines the importance of ribosome pausing to allow efficient regulation of protein expression and also of cotranslational subdomain folding.

scholarly journals Structure, function and antigenicity of the SARS-CoV-2 spike glycoprotein

2020 ◽  
Author(s):  
Alexandra C. Walls ◽  
Young-Jun Park ◽  
M. Alexandra Tortorici ◽  
Abigail Wall ◽  
Andrew T. McGuire ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Viral Entry ◽  
Neutralizing Antibodies ◽  
Target Cells ◽  
Furin Cleavage ◽  
Humoral Immune ◽  
Binding Domains ◽  
Furin Cleavage Site ◽  
Recent Emergence ◽  
Novel Coronavirus

SUMMARYThe recent emergence of a novel coronavirus associated with an ongoing outbreak of pneumonia (Covid-2019) resulted in infections of more than 72,000 people and claimed over 1,800 lives. Coronavirus spike (S) glycoprotein trimers promote entry into cells and are the main target of the humoral immune response. We show here that SARS-CoV-2 S mediates entry in VeroE6 cells and in BHK cells transiently transfected with human ACE2, establishing ACE2 as a functional receptor for this novel coronavirus. We further demonstrate that the receptor-binding domains of SARS-CoV-2 S and SARS-CoV S bind with similar affinities to human ACE2, which correlates with the efficient spread of SARS-CoV-2 among humans. We found that the SARS-CoV-2 S glycoprotein harbors a furin cleavage site at the boundary between the S1/S2 subunits, which is processed during biogenesis and sets this virus apart from SARS-CoV and other SARS-related CoVs. We determined a cryo-electron microscopy structure of the SARS-CoV-2 S ectodomain trimer, demonstrating spontaneous opening of the receptor-binding domain, and providing a blueprint for the design of vaccines and inhibitors of viral entry. Finally, we demonstrate that SARS-CoV S murine polyclonal sera potently inhibited SARS-CoV-2 S-mediated entry into target cells, thereby indicating that cross-neutralizing antibodies targeting conserved S epitopes can be elicited upon vaccination.

scholarly journals The expression of hACE2 receptor protein and its involvement in SARS-CoV-2 entry, pathogenesis, and its application as potential therapeutic target

Tumor Biology ◽  
2021 ◽  
Vol 43 (1) ◽  
pp. 177-196
Author(s):  
Lobna Al-Zaidan ◽  
Sarra Mestiri ◽  
Afsheen Raza ◽  
Maysaloun Merhi ◽  
Varghese Philipose Inchakalody ◽  
...  
Keyword(s):  
Binding Affinity ◽  
Receptor Binding ◽  
Virus Disease ◽  
Respiratory Illness ◽  
Host Cells ◽  
World Health ◽  
Receptor Protein ◽  
Unknown Etiology ◽  
Spike Glycoprotein ◽  
Binding Interface

Pneumonia cases of unknown etiology in Wuhan, Hubei province, China were reported to the World Health Organization on 31st of December 2019. Later the pathogen was reported to be a novel coronavirus designated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes Corona virus disease 2019 (COVID-19). The disease outspread was followed by WHO declaration of COVID-19 pandemic as a “Public Health Emergency of International Concern”. SARS-CoV-2 is a novel pathogenic beta coronavirus that infects humans causing severe respiratory illness. However, multifarious factors can contribute to the susceptibility to COVID-19 related morbidity and mortality such as age, gender, and underlying comorbidities. Infection initiates when viral particles bind to the host cell surface receptors where SARS-CoV-2 spike glycoprotein subunit 1 binds to the Angiotensin Converting Enzyme 2 (ACE2). It is of importance to mention that SARS-CoV and SARS-CoV-2 viruses’ mediate entry into the host cells via ACE2 receptor which might be correlated with the structural similarity of spike glycoprotein subunit 1 of both SARS viruses. However, the structural binding differs, whereas ACE2 receptor binding affinity with SARS-CoV-2 is 4 folds higher than that with SARS-CoV. Moreover, amino acids sequence divergence between the two S glycoproteins might be responsible for differential modulations of the specific immune response to both viruses. Identification of different aspects such as binding affinity, differential antigenic profiles of S-glycoproteins, and ACE2 mutations might influence the investigation of potential therapeutic strategies targeting SARS-CoV-2/ACE2 binding interface. In this review, we aim to elaborate on the expression of hACE2 receptor protein and its binding with SARS-CoV-2 S1 subunit, the possible immunogenic sequences of spike protein, effect of ACE 2 polymorphism on viral binding, and infectivity/susceptibility to disease. Furthermore, targeting of hACE2 receptor binding with SARS-CoV-2 S1 subunit via various mechanisms will be discussed to understand its role in therapeutics.

scholarly journals The fatty acid site is coupled to functional motifs in the SARS-CoV-2 spike protein and modulates spike allosteric behaviour

2021 ◽  
Author(s):  
Ana Sofia Oliveira ◽  
Deborah Shoemark ◽  
Amaurys Avila Ibarra ◽  
Andrew D. Davidson ◽  
Imre Berger ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Binding Site ◽  
Acid Site ◽  
Host Cells ◽  
Spike Protein ◽  
Nonequilibrium Molecular Dynamics ◽  
Binding Motif ◽  
Fatty Acid Binding ◽  
Furin Cleavage Site ◽  
Fatty Acid Binding Site

The SARS-CoV-2 spike protein is the first contact point between the SARS-CoV-2 virus and host cells and mediates membrane fusion. Recently, a fatty acid binding site was identified in the spike (Toelzer et al. Science 2020). The presence of linoleic acid at this site modulates binding of the spike to the human ACE2 receptor, stabilizing a locked conformation of the protein. Here, dynamical-nonequilibrium molecular dynamics simulations reveal that this fatty acid site is coupled to functionally relevant regions of the spike, some of them far from the fatty acid binding pocket. Removal of a ligand from the fatty acid binding site significantly affects the dynamics of distant, functionally important regions of the spike, including the receptor-binding motif, furin cleavage site and fusion-peptide-adjacent regions. The results also show significant differences in behaviour between clinical variants of the spike: e.g. the D614G mutation shows a significantly different conformational response for some structural motifs relevant for binding and fusion. The simulations identify structural networks through which changes at the fatty acid binding site are transmitted within the protein. These communication networks significantly involve positions that are prone to mutation, indicating that observed genetic variation in the spike may alter its response to linoleate binding and associated allosteric communication.

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