Structural views of SARS-CoV-2 spike-ACE2 complex. ACE2 in orange, spike RBD in pink. (A) Overall spike-ACE2 complex with ACE2 affinity-determinant positions identified by yeast display screening in purple. (B) Illustration of hydrogen bonds (yellow) formed between ACE2 Gln42 and spike Gly446 and Tyr449. Hydrogen atoms: white, oxygen: red, nitrogen: blue. (C) Absence of these hydrogen bonds for ACE2 Gln42Leu mutant. (D) Hydrophobic contacts (<5Å carbon atom separation-colored in cyan) between ACE2 Leu79 and spike Phe486. (E) Hydrophobic contacts between spike Phe486 and ACE2 Leu79Ile mutant. Figures generated from Protein Data Bank structure 6m0j (human ACE2) using Pymol.