Fig 2.

Positive selection of residues at the base of a key ACE2 glycan. (a) A linear schematic of the ACE2 protein is shown. Regions of the protein that interact with the SARS-CoV spike are indicated in dark gray (17). Residue positions found to be under positive selection in bats are shown with black tick marks. Six of these fall in the known surface of interaction with the SARS-CoV spike, and 13 more are indicated with numbers. Of these, five (in red type) are positioned at the base of a key glycan on the receptor that is located at position 90. (b) A rotated view of the structure shown in Fig. 1a, with the main SARS-CoV-binding surface now at the left. The glycosylated asparagine at position 90 is shown in orange, with five residues under positive selection sitting in a ridge adjacent to it (red).