Cryo-electron microscopy structure of the SADS-CoV spike glycoprotein provides insights into an evolution of unique coronavirus spike proteins

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Abstract

The current outbreak of Coronavirus Disease 2019 (COVID-19) by a novel betacoronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has aroused great public health concern. Coronavirus has a history of causing epidemics in human and animals. In 2017 an outbreak in piglets by a novel coronavirus was emerged designated as swine acute diarrhea syndrome coronavirus (SADS-CoV) which is originated from the same genus of horseshoe bats ( Rhinolophus ) as Severe Acute Respiratory Syndrome CoV (SARS-CoV) having a broad species tropism. In addition to human cells, it can also infect cell lines from diverse species. Coronavirus host range is determined by its spike glycoprotein (S). Given the importance of S protein in viral entry to cells and host immune responses, here we report the cryo-EM structure of the SADS-CoV S in the prefusion conformation at a resolution of 3.55 Å. Our study reveals that SADS-CoV S structure takes an intra-subunit quaternary packing mode where the NTD and CTD from the same subunit pack together by facing each other. The comparison of NTD and CTD with that of the other four genera suggests the evolutionary process of the SADS-CoV S. Moreover, SADS-CoV S has several characteristic structural features, such as more compact architecture of S trimer, and masking of epitopes by glycan shielding, which may facilitate viral immune evasion. These data provide new insights into the evolutionary relationships of SADS-CoV S and would extend our understanding of structural and functional diversity, which will facilitate to vaccine development.

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  1. SciScore for 10.1101/2020.03.04.976258: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    The automated software SerialEM was used to collect 1,000 movies at a defocus range of between 1.8 and 2.3 μm.
    SerialEM
    suggested: (SerialEM, RRID:SCR_017293)
    Image processing: Micrograph movie stacks were corrected for beam-induced motion using MotionCor2 [28].
    MotionCor2
    suggested: (MotionCor2, RRID:SCR_016499)
    The contrast transfer function parameters for each dose weighting image were determined with Gctf [29].
    Gctf
    suggested: (GCTF, RRID:SCR_016500)
    After iterative 2D-class average in RELION, only particles with best-resolved 2D averages were selected for initial model generation and 3D classification using RELION.
    RELION
    suggested: (RELION, RRID:SCR_016274)
    Chimera and PyMOL (https://pymol.org/) were used for graphical visualization [31].
    PyMOL
    suggested: (PyMOL, RRID:SCR_000305)
    Model building: Ab initio modeling of the spike protein was performed in Coot [32], using structure predictions calculated by Phyre2 [33], the partial structure modeled by EMBuilder [34], and the reference model (PDB: 5X58).
    Coot
    suggested: (Coot, RRID:SCR_014222)
    Phyre2
    suggested: None
    EMBuilder
    suggested: (EMBuilder, RRID:SCR_018557)

    Results from OddPub: Thank you for sharing your data.


    Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    Results from TrialIdentifier: No clinical trial numbers were referenced.


    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.


    Results from JetFighter: Please consider improving the rainbow (“jet”) colormap(s) used on page 34. At least one figure is not accessible to readers with colorblindness and/or is not true to the data, i.e. not perceptually uniform.


    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  2. SciScore for 10.1101/2020.03.04.976258: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    Antibodies
    SentencesResources
    The engagement of the CTDs of SARS S trimer helps it to keep one or more CTDs in the “stand up” position and facilitate the binding of ACE2 or neutralizing antibodies.
    ACE2
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    Numerous α-CoVs, for example, human CoV (HCoV-229E), utilize aminopeptidase N (APN) as its receptor, SARS-CoV, HCoV-NL63 and SARS-CoV-2 employ angiotensin-converting enzyme 2 (ACE2), and MERSCoV ties to dipeptidyl-peptidase 4 (DPP4).
    HCoV-NL63
    suggested: CVCL_RW88
    Software and Algorithms
    SentencesResources
    Structural evolution of coronavirus spike protein The S protein from all the four different genera of the CoVs packs a crown-like structure by three monomeric subunits, which can be divided into two packing modes: the cross-subunit packing mode and the intra-subunit packing mode [21].
    CoVs
    suggested: None
    The automated software SerialEM was used to collect 1,000 movies at a defocus range of between 1.8 and 2.3 µm.
    SerialEM
    suggested: (SerialEM, SCR_017293)
    Image processing Micrograph movie stacks were corrected for beam-induced motion using MotionCor2 [28].
    MotionCor2
    suggested: (MotionCor2, SCR_016499)
    The contrast transfer function parameters for each dose weighting image were determined with Gctf [29].
    Gctf
    suggested: (GCTF, SCR_016500)
    Reference-free 2D-class average was performed using RELION [30], and the well-resolved 2D averages were subjected to another iteration particle auto picking as a template with Gautomatch.
    RELION
    suggested: (RELION, SCR_016274)
    Chimera and PyMOL (https://pymol.org/) were used for graphical visualization [31].
    PyMOL
    suggested: (PyMOL, SCR_000305)
    Model building Ab initio modeling of the spike protein was performed in Coot [32], using structure predictions calculated by Phyre2 [33], the partial structure modeled by EMBuilder [34], and the reference model (PDB: 5X58).
    Coot
    suggested: (Coot, SCR_014222)
          <div style="margin-bottom:8px">
            <div><b>Phyre2</b></div>
            <div>suggested: None</div>
          </div>
        
          <div style="margin-bottom:8px">
            <div><b>EMBuilder</b></div>
            <div>suggested: (EMBuilder, <a href="https://scicrunch.org/resources/Any/search?q=SCR_018557">SCR_018557</a>)</div>
          </div>
        </td></tr></table>
    

    Results from OddPub: Thank you for sharing your data.


    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore is not a substitute for expert review. SciScore checks for the presence and correctness of RRIDs (research resource identifiers) in the manuscript, and detects sentences that appear to be missing RRIDs. SciScore also checks to make sure that rigor criteria are addressed by authors. It does this by detecting sentences that discuss criteria such as blinding or power analysis. SciScore does not guarantee that the rigor criteria that it detects are appropriate for the particular study. Instead it assists authors, editors, and reviewers by drawing attention to sections of the manuscript that contain or should contain various rigor criteria and key resources. For details on the results shown here, including references cited, please follow this link.