O-58 - SARS-CoV-2 RBD has six ACE2-contact residues, five differing from SARS-CoV
The SARS-CoV-2 receptor-binding domain carries six residues key to human-ACE2 binding (L455, F486, Q493, S494, N501, Y505); five of the six differ from the corresponding residues in SARS-CoV.
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Why this is evidence
H-43 (engineered) predicts a rationally chosen human-ACE2 interface; that five of the six SARS-CoV-2 contact residues differ from SARS-CoV — the characterised template — and instead match a natural pangolin donor (O-64) is what the natural genome of H-41/H-42 predicts. Discriminates H-43 from the two natural members; H-41 and H-42 share this genome and are not separated by it.