Structural analyses of the human ACE2 (PDB code 2AJF) with the modeled mouse (A) and rat (B) ones in cartoon diagrams and surface electrostatic potential maps. The regions 30–41, 82–84 and 353–357 are enlarged and the critical residues are labeled. The changed ones affecting the electrostatic potential are labeled and circled in dashed lines. The electrostatic potential is colored from −62 to +62 kiloteslas/charge.