scholarly journals N-Glycosylation of the SARS-CoV-2 Receptor Binding Domain Is Important for Functional Expression in Plants

2021 ◽  
Vol 12 ◽  
Author(s):  
Yun-Ji Shin ◽  
Julia König-Beihammer ◽  
Ulrike Vavra ◽  
Jennifer Schwestka ◽  
Nikolaus F. Kienzl ◽  
...  
Keyword(s):  
Protein Expression ◽  
Recombinant Proteins ◽  
Receptor Binding ◽  
Posttranslational Modifications ◽  
Functional Expression ◽  
Binding Domain ◽  
Site Directed Mutagenesis ◽  
Receptor Binding Domain ◽  
And Function ◽  
The Impact

Nicotiana benthamiana is used worldwide as production host for recombinant proteins. Many recombinant proteins such as monoclonal antibodies, growth factors or viral antigens require posttranslational modifications like glycosylation for their function. Here, we transiently expressed different variants of the glycosylated receptor binding domain (RBD) from the SARS-CoV-2 spike protein in N. benthamiana. We characterized the impact of variations in RBD-length and posttranslational modifications on protein expression, yield and functionality. We found that a truncated RBD variant (RBD-215) consisting of amino acids Arg319-Leu533 can be efficiently expressed as a secreted soluble protein. Purified RBD-215 was mainly present as a monomer and showed binding to the conformation-dependent antibody CR3022, the cellular receptor angiotensin converting enzyme 2 (ACE2) and to antibodies present in convalescent sera. Expression of RBD-215 in glycoengineered ΔXT/FT plants resulted in the generation of complex N-glycans on both N-glycosylation sites. While site-directed mutagenesis showed that the N-glycans are important for proper RBD folding, differences in N-glycan processing had no effect on protein expression and function.

scholarly journals Design of a companion bioinformatic tool to detect the emergence and geographical distribution of SARS-CoV-2 Spike protein genetic variants

2020 ◽  
Vol 18 (1) ◽  
Author(s):  
Alice Massacci ◽  
Eleonora Sperandio ◽  
Lorenzo D’Ambrosio ◽  
Mariano Maffei ◽  
Fabio Palombo ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Consensus Sequence ◽  
Cell Epitope ◽  
Vaccine Design ◽  
Binding Domain ◽  
Spike Protein ◽  
Antibody Activity ◽  
Binding Motif ◽  
Receptor Binding Domain ◽  
The Impact

Abstract Background Tracking the genetic variability of Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) is a crucial challenge. Mainly to identify target sequences in order to generate robust vaccines and neutralizing monoclonal antibodies, but also to track viral genetic temporal and geographic evolution and to mine for variants associated with reduced or increased disease severity. Several online tools and bioinformatic phylogenetic analyses have been released, but the main interest lies in the Spike protein, which is the pivotal element of current vaccine design, and in the Receptor Binding Domain, that accounts for most of the neutralizing the antibody activity. Methods Here, we present an open-source bioinformatic protocol, and a web portal focused on SARS-CoV-2 single mutations and minimal consensus sequence building as a companion vaccine design tool. Furthermore, we provide immunogenomic analyses to understand the impact of the most frequent RBD variations. Results Results on the whole GISAID sequence dataset at the time of the writing (October 2020) reveals an emerging mutation, S477N, located on the central part of the Spike protein Receptor Binding Domain, the Receptor Binding Motif. Immunogenomic analyses revealed some variation in mutated epitope MHC compatibility, T-cell recognition, and B-cell epitope probability for most frequent human HLAs. Conclusions This work provides a framework able to track down SARS-CoV-2 genomic variability.

scholarly journals Identification of residues in the receptor-binding domain (RBD) of the spike protein of human coronavirus NL63 that are critical for the RBD–ACE2 receptor interaction

2008 ◽  
Vol 89 (4) ◽  
pp. 1015-1024 ◽  
Author(s):  
Han-Xin Lin ◽  
Yan Feng ◽  
Gillian Wong ◽  
Liping Wang ◽  
Bei Li ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Binding Domain ◽  
Site Directed Mutagenesis ◽  
Spike Protein ◽  
Receptor Interaction ◽  
Receptor Binding Domain ◽  
Human Coronavirus ◽  
C Terminus ◽  
Group I ◽  
Truncated Variants

Human coronavirus NL63 (NL63), a member of the group I coronaviruses, may cause acute respiratory diseases in young children and immunocompromised adults. Like severe acute respiratory syndrome coronavirus (SARS-CoV), NL63 also employs the human angiotensin-converting enzyme 2 (hACE2) receptor for cellular entry. To identify residues in the spike protein of NL63 that are important for hACE2 binding, this study first generated a series of S1-truncated variants, examined their associations with the hACE2 receptor and subsequently mapped a minimal receptor-binding domain (RBD) that consisted of 141 residues (aa 476–616) towards the C terminus of the S1 domain. The data also demonstrated that the NL63 RBD bound to hACE2 more efficiently than its full-length counterpart and had a binding efficiency comparable to the S1 or RBD of SARS-CoV. A further series of RBD variants was generated using site-directed mutagenesis and random mutant library screening assays, and identified 15 residues (C497, Y498, V499, C500, K501, R518, R530, V531, G534, G537, D538, S540, E582, W585 and T591) that appeared to be critical for the RBD–hACE2 association. These critical residues clustered in three separate regions (designated RI, RII and RIII) inside the RBD, which may represent three receptor-binding sites. These results may help to delineate the molecular interactions between the S protein of NL63 and the hACE2 receptor, and may also enhance our understanding of the pathogenesis of NL63 and SARS-CoV.

scholarly journals Structures and function of locked conformations of SARS-CoV-2 spike

2021 ◽  
Author(s):  
Kun Qu ◽  
Xiaoli Xiong ◽  
Katarzyna A. Ciazynska ◽  
Andrew P. Carter ◽  
John A. G. Briggs
Keyword(s):  
Receptor Binding ◽  
Functional Characterization ◽  
Protein S ◽  
Binding Domain ◽  
Receptor Binding Domain ◽  
Neutral Ph ◽  
And Function ◽  
Cellular Compartments ◽  
Domain Dynamics ◽  
Spike Dynamics

AbstractThe spike protein (S) of SARS-CoV-2 has been observed in three distinct pre-fusion conformations: locked, closed and open. Of these, the locked conformation was not previously observed for SARS-CoV-1 S and its function remains poorly understood. Here we engineered a SARS-CoV-2 S protein construct “S-R/x3” to arrest SARS-CoV-2 spikes in the locked conformation by a disulfide bond. Using this construct we determined high-resolution structures revealing two distinct locked states, with or without the D614G substitution that has become fixed in the globally circulating SARS-CoV-2 strains. The D614G mutation induces a structural change in domain D from locked-1 to locked-2 conformation to alter spike dynamics, promoting transition into the closed conformation from which opening of the receptor binding domain is permitted. The transition from locked to closed conformations is additionally promoted by a change from low to neutral pH. We propose that the locked conformations of S are present in the acidic cellular compartments where virus is assembled and egresses. In this model, release of the virion into the neutral pH extracellular space would favour transition to the closed form which itself can stochastically transition into the open form. The S-R/x3 construct provides a tool for the further structural and functional characterization of the locked conformations of S, as well as how sequence changes might alter S assembly and regulation of receptor binding domain dynamics.

scholarly journals Epistasis at the SARS-CoV-2 RBD Interface and the Propitiously Boring Implications for Vaccine Escape

2021 ◽  
Author(s):  
Nash D. Rochman ◽  
Guilhem Faure ◽  
Yuri I. Wolf ◽  
Peter L. Freddolino ◽  
Feng Zhang ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
Binding Domain ◽  
Receptor Binding Domain ◽  
Wild Type ◽  
Protein Structure Modeling ◽  
Escape Mutants ◽  
Small Set ◽  
Global Concern ◽  
The Impact

AbstractAt the time of this writing, August 2021, potential emergence of vaccine escape variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a grave global concern. The interface between the receptor-binding domain (RBD) of SARS-CoV-2 spike (S) protein and the host receptor (ACE2) overlap with the binding site of principal neutralizing antibodies (NAb), limiting the repertoire of viable mutations. Nonetheless, variants with multiple mutations in the RBD have rose to dominance. Non-additive, epistatic relationships among RBD mutations are apparent, and assessing the impact of such epistasis on the mutational landscape is crucial. Epistasis can substantially increase the risk of vaccine escape and cannot be completely characterized through the study of the wild type (WT) alone. We employed protein structure modeling using Rosetta to compare the effects of all single mutants at the RBD-NAb and RBD-ACE2 interfaces for the WT, Gamma (417T, 484K, 501Y), and Delta variants (452R, 478K). Overall, epistasis at the RBD surface appears to be limited and the effects of most multiple mutations are additive. Epistasis at the Delta variant interface weakly stabilizes NAb interaction relative to ACE2, whereas in the Gamma variant, epistasis more substantially destabilizes NAb interaction. These results suggest that the repertoire of potential escape mutations for the Delta variant is not substantially different from that of the WT, whereas Gamma poses a moderately greater risk for enhanced vaccine escape. Thus, the modest ensemble of mutations relative to the WT shown to reduce vaccine efficacy might constitute the majority of all possible escape mutations.SignificancePotential emergence of vaccine escape variants of SARS-CoV-2 is arguably the most pressing problem during the COVID-19 pandemic as vaccines are distributed worldwide. We employed a computational approach to assess the risk of antibody escape resulting from mutations in the receptor-binding domain of the spike protein of the wild type SARS-CoV-2 virus as well as the Gamma and Delta variants. The results indicate that emergence of escape mutants is somewhat less likely for the Delta variant than for the wild type and moderately more likely for the Gamma variant. We conclude that the small set of escape-enhancing mutations already identified for the wild type is likely to include the majority of all possible mutations with this effect, a welcome finding.

scholarly journals Comprehensive mapping of mutations to the SARS-CoV-2 receptor-binding domain that affect recognition by polyclonal human serum antibodies

2021 ◽  
Author(s):  
Allison J. Greaney ◽  
Andrea N. Loes ◽  
Katharine H.D. Crawford ◽  
Tyler N. Starr ◽  
Keara D. Malone ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Binding Domain ◽  
Binding Motif ◽  
Human Antibody ◽  
Receptor Binding Domain ◽  
Serum Antibodies ◽  
Main Target ◽  
The Impact ◽  
Polyclonal Serum ◽  
Comprehensive Mapping

AbstractThe evolution of SARS-CoV-2 could impair recognition of the virus by human antibody-mediated immunity. To facilitate prospective surveillance for such evolution, we map how convalescent serum antibodies are impacted by all mutations to the spike’s receptor-binding domain (RBD), the main target of serum neutralizing activity. Binding by polyclonal serum antibodies is affected by mutations in three main epitopes in the RBD, but there is substantial variation in the impact of mutations both among individuals and within the same individual over time. Despite this inter- and intra-person heterogeneity, the mutations that most reduce antibody binding usually occur at just a few sites in the RBD’s receptor binding motif. The most important site is E484, where neutralization by some sera is reduced >10-fold by several mutations, including one in emerging viral lineages in South Africa and Brazil. Going forward, these serum escape maps can inform surveillance of SARS-CoV-2 evolution.

scholarly journals SARS-CoV-2 Variant of Concern Substitutions Alter Spike Glycoprotein Receptor Binding Domain Structure and Stability

2021 ◽  
Author(s):  
Daniel L Moss ◽  
Jay Rappaport
Keyword(s):  
Receptor Binding ◽  
Rapid Development ◽  
Structure And Function ◽  
Binding Domain ◽  
Amino Acid Substitutions ◽  
Receptor Binding Domain ◽  
Spike Glycoprotein ◽  
Structure And Stability ◽  
The World ◽  
And Function

The emergence of severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) and the subsequent COVID-19 pandemic has significantly impacted the world not just with disease and death but also economic turmoil. The rapid development and deployment of extremely effective vaccines against SARS-CoV-2 has made the end of the pandemic a reality within reach. However, as the virus spreads it has acquired mutations; and thus, variants of concern have emerged that are more infectious and reduce the efficacy of existing vaccines. While promising efforts are underway to combat these variants, the evolutionary pressures leading to these variants are poorly understood. To that end, here we have studied the effects of three amino-acid substitutions on the structure and function of the SARS-CoV-2 spike glycoprotein receptor-binding domain found in several variants of concern such as B.1.1.7, B.1.351 and P.1 that are now circulating. We found that these substitutions alter the RBD structure and stability, as well as its ability to bind to ACE2, which may have opposing and compensatory effects. These findings provide new insights into how these Variants of Concern (VOC) may have been selected to optimize infectivity while maintaining the structure and stability of the receptor binding domain.

scholarly journals Comprehensive Functional Analysis of N-Linked Glycans on Ebola Virus GP1

mBio ◽  
2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Nicholas J. Lennemann ◽  
Bethany A. Rhein ◽  
Esther Ndungo ◽  
Kartik Chandran ◽  
Xiangguo Qiu ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Ebola Virus ◽  
Binding Domain ◽  
Marburg Virus ◽  
Viral Envelope ◽  
Targeted Mutagenesis ◽  
Site Directed Mutagenesis ◽  
Receptor Binding Domain ◽  
Antibody Neutralization ◽  
Glycosylation Sites

ABSTRACTEbola virus (EBOV) entry requires the virion surface-associated glycoprotein (GP) that is composed of a trimer of heterodimers (GP1/GP2). The GP1 subunit contains two heavily glycosylated domains, the glycan cap and the mucin-like domain (MLD). The glycan cap contains only N-linked glycans, whereas the MLD contains both N- and O-linked glycans. Site-directed mutagenesis was performed on EBOV GP1 to systematically disrupt N-linked glycan sites to gain an understanding of their role in GP structure and function. All 15 N-glycosylation sites of EBOV GP1 could be removed without compromising the expression of GP. The loss of these 15 glycosylation sites significantly enhanced pseudovirion transduction in Vero cells, which correlated with an increase in protease sensitivity. Interestingly, exposing the receptor-binding domain (RBD) by removing the glycan shield did not allow interaction with the endosomal receptor, NPC1, indicating that the glycan cap/MLD domains mask RBD residues required for binding. The effects of the loss of GP1 N-linked glycans on Ca2+-dependent (C-type) lectin (CLEC)-dependent transduction were complex, and the effect was unique for each of the CLECs tested. Surprisingly, EBOV entry into murine peritoneal macrophages was independent of GP1 N-glycans, suggesting that CLEC-GP1 N-glycan interactions are not required for entry into this important primary cell. Finally, the removal of all GP1 N-glycans outside the MLD enhanced antiserum and antibody sensitivity. In total, our results provide evidence that the conserved N-linked glycans on the EBOV GP1 core protect GP from antibody neutralization despite the negative impact the glycans have on viral entry efficiency.IMPORTANCEFilovirus outbreaks occur sporadically throughout central Africa, causing high fatality rates among the general public and health care workers. These unpredictable hemorrhagic fever outbreaks are caused by multiple species of Ebola viruses, as well as Marburg virus. While filovirus vaccines and therapeutics are being developed, there are no licensed products. The sole viral envelope glycoprotein, which is a principal immunogenic target, contains a heavy shield of glycans surrounding the conserved receptor-binding domain. We find that disruption of this shield through targeted mutagenesis leads to an increase in cell entry, protease sensitivity, and antiserum/antibody sensitivity but is not sufficient to allow virion binding to the intracellular receptor NPC1. Therefore, our studies provide evidence that filoviruses maintain glycoprotein glycosylation to protect against proteases and antibody neutralization at the expense of efficient entry. Our results unveil interesting insights into the unique entry process of filoviruses and potential immune evasion tactics of the virus.

scholarly journals Disulfide bonds play a critical role in the structure and function of the receptor-binding domain of the SARS-CoV-2 Spike antigen

2021 ◽  
pp. 167357
Author(s):  
Andrey M. Grishin ◽  
Nataliya V. Dolgova ◽  
Shelby Landreth ◽  
Olivier Fisette ◽  
Ingrid J. Pickering ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Disulfide Bonds ◽  
Critical Role ◽  
Structure And Function ◽  
Binding Domain ◽  
Receptor Binding Domain ◽  
And Function

scholarly journals Structural and energetic profiling of SARS-CoV-2 receptor binding domain antibody recognition and the impact of circulating variants

2021 ◽  
Vol 17 (9) ◽  
pp. e1009380
Author(s):  
Rui Yin ◽  
Johnathan D. Guest ◽  
Ghazaleh Taherzadeh ◽  
Ragul Gowthaman ◽  
Ipsa Mittra ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
Binding Domain ◽  
Receptor Binding Domain ◽  
Design Strategies ◽  
Detailed Structure ◽  
Antibody Recognition ◽  
Domain Antibody ◽  
The Impact ◽  
Binding Determinants

The SARS-CoV-2 pandemic highlights the need for a detailed molecular understanding of protective antibody responses. This is underscored by the emergence and spread of SARS-CoV-2 variants, including Alpha (B.1.1.7) and Delta (B.1.617.2), some of which appear to be less effectively targeted by current monoclonal antibodies and vaccines. Here we report a high resolution and comprehensive map of antibody recognition of the SARS-CoV-2 spike receptor binding domain (RBD), which is the target of most neutralizing antibodies, using computational structural analysis. With a dataset of nonredundant experimentally determined antibody-RBD structures, we classified antibodies by RBD residue binding determinants using unsupervised clustering. We also identified the energetic and conservation features of epitope residues and assessed the capacity of viral variant mutations to disrupt antibody recognition, revealing sets of antibodies predicted to effectively target recently described viral variants. This detailed structure-based reference of antibody RBD recognition signatures can inform therapeutic and vaccine design strategies.

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