PT  - JOURNAL ARTICLE
AU  - Javeed Ahmad
AU  - Jiansheng Jiang
AU  - Lisa F. Boyd
AU  - Kannan Natarajan
AU  - David H. Margulies
TI  - Synthetic nanobody–SARS-CoV-2 receptor-binding domain structures identify distinct epitopes
AID  - 10.1101/2021.01.27.428466
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.01.27.428466
4099  - http://biorxiv.org/content/early/2021/01/27/2021.01.27.428466.short
4100  - http://biorxiv.org/content/early/2021/01/27/2021.01.27.428466.full
AB  - 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.Competing Interest StatementThe authors have declared no competing interest.