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

BioRxiv : the Preprint Server for Biology
Javeed AhmadDavid H Margulies


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. 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.

Methods Mentioned

surface plasmon resonance

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