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

Fig. 6. Analysis of S-GSAS-D614G-K417N-E484K-N501Y (“triple mutant spike”) and S-GSAS-B.1.351 (B.1.351 spike).

Fig. 6.

(A and B) Cryo-EM reconstructions of (A) triple mutant spike and (B) B.1.351 spike, in rainbow colors. (C) Binding 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 the B.1.351 spike 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) Cartoon helix and sheet secondary structure elements of the triple mutant spike variant SD2 aligned S1 protomers (left) and B.1.351 variant SD2 aligned S1 protomers (right). (E) Angle and dihedral measures for the interprotomer SD2-SD1-NTD′ network. From left to right: RBD to adjacent NTD distance, NTD′-to-SD2 angle, SD1-to-NTD′ dihedral, and NTD′-to-SD2 dihedral.