Synthetic nanobody–SARS-CoV-2 receptor-binding domain structures identify distinct epitopes

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Abstract

The worldwide spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) demands unprecedented attention. We report four X-ray crystal structures of three synthetic nanobodies (sybodies) (Sb16, Sb45 and Sb68) bind to the receptor-binding domain (RBD) of SARS-CoV-2: binary complexes of Sb16–RBD and Sb45–RBD; a ternary complex of Sb45–RBD–Sb68; and Sb16 unliganded. Sb16 and Sb45 bind the RBD at the ACE2 interface, positioning their CDR2 and CDR3 loops diametrically. Sb16 reveals a large CDR2 shift when binding the RBD. Sb68 interacts peripherally at the ACE2 interface; steric clashes with glycans explain its mechanism of viral neutralization. Superposing these structures onto trimeric spike (S) protein models indicates these sybodies bind conformations of the mature S protein differently, which may aid therapeutic design.

One Sentence Summary

X-ray structures of synthetic nanobodies complexed with the receptor-binding domain of the spike protein of SARS-CoV-2 reveal details of CDR loop interactions in recognition of distinct epitopic sites.

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  1. SciScore for 10.1101/2021.01.27.428466: (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

    Experimental Models: Organisms/Strains
    SentencesResources
    Graded and increasing concentrations of SB16, SB45 and SB68 were injected over the RBD-immobilized surface at a flow rate of 30 μl/min with an association time of 120 s and dissociation time of 2000 s.
    SB45
    suggested: None
    Software and Algorithms
    SentencesResources
    Subsequent refinements were carried out with PHENIX (44).
    PHENIX
    suggested: (Phenix, RRID:SCR_014224)
    CDR loops were manually rebuilt by fitting to the electron density maps with Coot (45).
    Coot
    suggested: (Coot, RRID:SCR_014222)
    Illustrations and calculations of superpositioned models were prepared in PyMOL (The PyMOL Molecular Graphics System, Version 2.4.0 Schrodinger, LLC).
    PyMOL
    suggested: (PyMOL, RRID:SCR_000305)
    Calculation of hinge relationships of domains was accomplished with HINGE (https://niaidsis.niaid.nih.gov/hinge.html), provided courtesy of Peter Sun, NIAID.
    HINGE
    suggested: (Hinge, RRID:SCR_016135)
    Buried surface area (BSA) calculations were performed with PISA (https://www.ebi.ac.uk/pdbe/pisa/).
    PISA
    suggested: (PISA, RRID:SCR_015749)

    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: We did not find any issues relating to colormaps.


    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

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