Extended Data Fig. 4 |. Fusion activity of mutants of interest.

a,b, Flow cytometry plots (a) and micrographs (b) of S-expressing cells with fusion-incompetent mutations at 3 hours post-mixing with hACE2-expressing cells. c,d, Flow cytometry plots (c) and micrographs (d) of S-expression cells with fusion-enhancing mutations at 3 post-mixing with hACE2-expressing cells. e,f, Flow cytometry plots (e) and micrographs (f) of S-expression cells with combinations of fusion-incompetent mutations at 3 hours post-mixing with hACE2-expressing cells. Plots and micrographs are representative of n = 2 independent replicates. Abbreviations of combinatorial mutations are as follows: 2P, K986P/V987P; 2PQ, K986P/V987P/D994Q; 2PR, K986P/V987P/Q1005R; 2PQR, K986P/V987P/D994Q/Q1005R. Scale bar: 100 μm.