Fig. 2: Structural analysis of R1-26 epitope binding and biochemical activities of R1-26.

a Structures (low-pass filtered to 12 Å) of S-GSAS/6P S-trimers in complex with R1-26 Fabs in different stoichiometries. R1-26 Fab, NTD and RBD are highlighted in magenta, blue and cyan, respectively; the rest of the S-trimer is colored gray. b Epitope of R1-26 on spike RBD. R1-26-H and R1-26-L chains are colored in magenta and purple. Detailed interactions between R1-26 and RBD are shown in the dashed boxes. CDR loops are indicated, selected interacting residues in antibody-RBD interface are shown. Thick and thin dashed lines indicate cation-π and hydrogen bond interactions; The solid line represents a salt bridge. c Ligand-induced conformational change assays to probe the induction of post-fusion structures, presence of proteinase K resistance core is indicative of post-fusion structure^16,43,103. d R1-26 inhibits spike-ACE2 interaction mediated cell-cell membrane fusion (data are presented as mean values ± SD, n = 3). Two-tailed paired student’s t test was performed. Source data for c and d are provided as a Source Data file.