Homology analysis of the spike proteins of SARS-CoVs and related Bat-CoVs
Phylogenetic analysis of the spike protein sequences of SARS-CoV-2 and Bat-CoVs, SARS-CoV is shown in Figure 1(Fig. 1). The results are in agreement with recent reports of an independent introduction of SARS-CoV-2 from a Bat-CoV, different from the spillover which led to the introduction of SARS-CoV, being the Bat-CoV of Rhinolophus affinis the probable ancestor of this new virus (Wong et al., 2020[18]). Indeed, the sequences of the whole spike of this Bat-CoV and of SARS-CoV-2 share 97.7 % identity (Figure 1(Fig. 1)). More divergence is found however in the S1 subunit, particularly in the Receptor Binding Domain (RBD) of the different spike proteins. SARS-CoV and Bat-CoV from Rhinolophus sinicus (originally signaled as the most closely related virus to SARS-CoV-2) exhibit several amino acid substitutions and deletions in the RBD compared to SARS-CoV-2. The RBD of Bat-CoV from Rhinolophus affinis, although more closely related to the one of SAS-CoV-2, also displayed several amino acid substitutions (Figure 2(Fig. 2)).