Cryo-EM structure of SARS-CoV-2 NSP15 NendoU at pH 6.0
Ontology highlight
ABSTRACT:
SUBMITTER: Andre Schutzer Godoy
PROVIDER: EMPIAR-10794 | biostudies-other |
REPOSITORIES: biostudies-other
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Project description:The omicron variant of SARS-CoV-2 has been spreading rapidly across the globe. The virus-surface spike protein plays a critical role in the cell entry and immune evasion of SARS-CoV-2. Here we determined the 3.0 Å cryo-EM structure of the omicron spike protein ectodomain. In contrast to the original strain of SARS-CoV-2 where the receptor-binding domain (RBD) of the spike protein takes a mixture of open ("standing up") and closed ("lying down") conformations, the omicron spike molecules are predominantly in the open conformation, with one upright RBD ready for receptor binding. The open conformation of the omicron spike is stabilized by enhanced inter-domain and inter-subunit packing, which involves new mutations in the omicron strain. Moreover, the omicron spike has undergone extensive mutations in RBD regions where known neutralizing antibodies target, allowing the omicron variant to escape immune surveillance aimed at the original viral strain. The stable open conformation of the omicron spike sheds light on the cell entry and immune evasion mechanisms of the omicron variant.
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Project description:Global emergencies caused by the severe acute respiratory syndrome coronavirus (SARS-CoV), Middle-East respiratory syndrome coronavirus (MERS-CoV) and SARS-CoV-2 significantly endanger human health. The spike (S) glycoprotein is the key antigen and its conserved S2 subunit contributes to viral entry by mediating host-viral membrane fusion. However, structural information of the post-fusion S2 from these highly pathogenic human-infecting coronaviruses is still lacking. We used single-particle cryo-electron microscopy to show that the post-fusion SARS-CoV S2 forms a further rotated HR1-HR2 six-helix bundle and a tightly bound linker region upstream of the HR2 motif. The structures of pre- and post-fusion SARS-CoV S glycoprotein dramatically differ, resembling that of the Mouse hepatitis virus (MHV) and other class I viral fusion proteins. This structure suggests potential targets for the development of vaccines and therapies against a wide range of SARS-like coronaviruses.
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Project description:Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus that causes the coronavirus disease 2019 (COVID-19). SARS-CoV-2 encodes three putative ion channels: E, 8a, and 3a1,2. 3a is expressed in SARS patient tissue and anti-3a antibodies are observed in patient plasma3-6. 3a has been implicated in viral release7, inhibition of autophagy8, inflammasome activation9, and cell death10,11 and its deletion reduces viral titer and morbidity in mice1, raising the possibility that 3a could be an effective vaccine or therapeutic target3,12. Here, we present the first cryo-EM structures of SARS-CoV-2 3a to 2.1 Å resolution and demonstrate 3a forms an ion channel in reconstituted liposomes. The structures in lipid nanodiscs reveal 3a dimers and tetramers adopt a novel fold with a large polar cavity that spans halfway across the membrane and is accessible to the cytosol and the surrounding bilayer through separate water- and lipid-filled openings. Electrophysiology and fluorescent ion imaging experiments show 3a forms Ca2+-permeable non-selective cation channels. We identify point mutations that alter ion permeability and discover polycationic inhibitors of 3a channel activity. We find 3a-like proteins in multiple Alphacoronavirus and Betacoronavirus lineages that infect bats and humans. These data show 3a forms a functional ion channel that may promote COVID-19 pathogenesis and suggest targeting 3a could broadly treat coronavirus diseases.
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| EMPIAR-11815 | biostudies-other
Project description:The COVID-19 pandemic prompted an unprecedented effort to develop effective countermeasures against SARS-CoV-2. While efficacious vaccines and certain therapeutic monoclonal antibodies are available, here, we report the development, cryo-EM structures and functional analyses of distinct potent monoclonal antibodies (mAbs) that neutralize SARS-CoV-2 and its variant B.1.351. We established a platform for rapid identification of highly potent and specific SARS-CoV-2-neutralizing antibodies by high-throughput B cell receptor single cell sequencing of spike receptor binding domain immunized animals. We identified two highly potent and specific SARS-CoV-2 neutralizing mAb clones that have single-digit nanomolar affinity and low-picomolar avidity. We also generated a bispecific antibody of these two lead clones. The lead monospecific and bispecific antibodies showed strong neutralization ability against prototypical SARS-CoV-2 and the highly contagious South African variant B.1.351 that post a further risk of reducing the efficacy of currently available therapeutic antibodies and vaccines. The lead mAbs showed potent in vivo efficacy against authentic SARS-CoV-2 in both prophylactic and therapeutic settings. We solved five cryo-EM structures at ~3 resolution of these neutralizing antibodies in complex with the ectodomain of the prefusion spike trimer, and revealed the molecular epitopes, binding patterns and conformations between the antibodies and spike RBD, which are distinct from existing antibodies. Our recently developed antibodies expand the repertoire of the toolbox of COVID-19 countermeasures against the SARS-CoV-2 pathogen and its emerging variants.
2022-01-11 | GSE174635 | GEO
Project description:New therapeutics are urgently needed to inhibit SARS-CoV-2, the virus responsible for the on-going Covid-19 pandemic. Nsp15, a uridine-specific endoribonuclease found in all coronaviruses, processes viral RNA to evade detection by RNA-activated host defense systems, making it a promising drug target. Previous work with SARS-CoV-1 established that Nsp15 is active as a hexamer, yet how Nsp15 recognizes and processes viral RNA remains unknown. Here we report a series of cryo-EM reconstructions of SARS-CoV-2 Nsp15. The UTP-bound cryo-EM reconstruction at 3.36 Å resolution provides molecular details into how critical residues within the Nsp15 active site recognize uridine and facilitate catalysis of the phosphodiester bond, whereas the apo-states reveal active site conformational heterogeneity. We further demonstrate the specificity and mechanism of nuclease activity by analyzing Nsp15 products using mass spectrometry. Collectively, these findings advance understanding of how Nsp15 processes viral RNA and provide a structural framework for the development of new therapeutics.
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