Fig. 10. The origin and features of the spike protein receptor binding domain of SARS-CoV-2. A. Zoonotic evolution of SARS-CoV-2, SARS CoV and MERS CoV. B. Sequence alignment of the spike protein of SARS-CoV-2, bat and pangolin CoV. C. Structure and amino acid sequence of the furin recognition motif observed only in human SARS-CoV-2 spike protein.