Fig. 3: Analysis of the RBD sequence.

a, Sequence alignment showing the RBD in human, pangolin and bat coronaviruses. The five critical residues for binding between SARS-CoV RBD and human ACE2 protein are indicated in red boxes, and ACE2-contacting residues are indicated by yellow boxes as previously described⁹. In the Guangdong pangolin-CoV sequence, the codon positions encoding the amino acids Pro337, Asn420, Pro499 and Asn519 have ambiguous nucleotide compositions, resulting in possible alternative amino acids at these sites (threonine, glycine, threonine and lysine, respectively). Sequence gaps are indicated with dashes. The short black lines at the top indicate the positions of every 10 residues. GD, Guangdong; GX, Guangxi. b, Phylogenetic trees of the SARS-CoV-2-related lineage estimated from the entire RBD region (top) and synonymous sites only (bottom). Branch supports obtained from 1,000 bootstrap replicates are shown. Branch scale bars are shown as 0.1 substitutions per site.