Figure 5.

Mutation Effects in the Context of RBD Structure and Implications for Sarbecovirus Evolution

(A and B) Mutational constraint mapped to the SARS-CoV-2 RBD structure. A sphere at each site C_ɑ is colored according to the mean effect of mutations with respect to expression (A) or binding (B), with red indicating more constraint. RBD structural features and the ACE2 K31 and K353 interaction hotspot residues are labeled. Yellow sticks indicate disulfide bridges. Interactive structure-based visualizations of these data are at https://jbloomlab.github.io/SARS-CoV-2-RBD_DMS/structures/.

(C) Relationship between mutational constraint on binding and expression. The structural view shows sites that are under strong constraint for ACE2 binding but are tolerant of mutations for expression (cyan spheres).

(D) Heatmap as in Figure 3B, subsetted on sites that directly contact ACE2 in the SARS-CoV-2 or SARS-CoV-1 RBD structures, plus interface site 494, which is a key site of adaptation in SARS-CoV-1.

(E) RBD sites 493, 498, and 501, which have many affinity-enhancing mutations, participate in polar contact networks involving the ACE2 interaction hotspot residues K31 and K353.

(F) Variation at ACE2 contact sites in sarbecovirus RBDs. Circles show the effects of individual mutations that differentiate a virus ACE2 interface from SARS-CoV-2, while x shows the mean effect of all mutations at that site. The sum of individual mutation effects at interface residues is shown, compared to the actual RBD binding relative to unmutated SARS-CoV-2.

See also Figure S5.