Fig. 4.

Comparisons of phylogenetic relationships among host receptors and enzymes. Phylogenetic comparison of A ACE2, B APN, C TMPRSS2, D SAS, E DPP4, F cathepsin L/procathepsin L and G furin among various host species. Generally, the phylogenetic segregation of host enzymes and receptors followed the species-related pattern except for the ACE2 enzyme, which also showed the highest genetic variation scale of 0.10. H Comparison of the key amino acids in human ACE2 projected to interact with the receptor binding domain of the S protein of SARS-CoV-2. Shaded in dark gray and arrowed in red are the positions and the single letter codes of the 20 amino acids and 5 critical residues, respectively, required for successful S protein attachment. The proportion of amino acids that overlap with the twenty required (/20) and the 5 critical (/5) residues are shown on the right in blue and red, respectively. The fractional scores for cattle and white-tailed deer are colored in aqua