Mutations across SARS-CoV-2 S sequences. (A) Structure of SARS-CoV (5 × 58) (shown instead of SARS-CoV-2 for completeness of the Receptor Binding Motif [RBM]). (B–D) The three protomers in the closed SARS-CoV-2 S glycoprotein (Protein Data Bank ID code 6VXX) are colored in yellow, cyan, and white.