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. 2021 Aug 6;373(6555):eabi6226. doi: 10.1126/science.abi6226

Fig. 5. Antigenic and conformational analysis of the RBD E484K substitution.

Fig. 5.

(A) Binding of RBD-directed antibodies DH1041, DH1043, and DH1047 and NTD-directed antibodies DH1050.1 and DH1052 to WT RBD, RBD-K417N, RBD-N501Y, and RBD-E484K, measured by SPR. (B) Binding of ACE2; RBD-directed antibodies DH1041, DH1043, and DH1047; and NTD-directed antibodies DH1050.1 and DH1052 to spike variants, measured by SPR. The black dotted lines represent D614G spike binding levels. (C) Binding of ACE2 receptor ectodomain (RBD-directed) and antibodies DH1041 and DH1047 (RBD-directed, neutralizing), DH1050.1 (NTD-directed, neutralizing), and DH1052 (NTD-directed, non-neutralizing) to S-GSAS-D614G-E484K (top row) and S-GSAS-D614G-K417N-E484K-N501Y (“triple mutant spike”) (bottom row), measured by SPR using single-cycle kinetics. The red lines are the binding sensorgrams; the black lines show fits of the data to a 1:1 Langmuir binding model. The on-rate (kon, M–1 s–1), off-rate (koff, s–1), and affinity (KD, nM) for each interaction are indicated. The binding of DH1047 to spike was too tight to allow accurate affinity measurement. (D and E) State probabilities from the WT RBD [(D), left] and the K417N-E484K-N501Y variant RBD [(E), left] Markov model stationary distribution. Error bars indicate the 95% confidence interval. The Hook and Disordered states of the WT RBD with 25 configurations are shown in translucent gray [(D), right)]. The K417N-E484K-N501Y variant RBD Hook and Disordered states with 25 configurations are shown in translucent gray [(E), right)]. Residue 484 is depicted in stick representation.