A hexapeptide of the receptor-binding domain of SARS corona virus spike protein blocks viral entry into host cells via the human receptor ACE2.

In vitro infection of Vero E6 cells by SARS coronavirus (SARS-CoV) is blocked by hexapeptide Tyr-Lys-Tyr-Arg-Tyr-Leu. The peptide also inhibits proliferation of coronavirus NL63. On human cells both viruses utilize angiotensin-converting enzyme 2 (ACE2) as entry receptor. Blocking the viral entry is specific as alpha virus Sindbis shows no reduction in infectivity. Peptide 438YKYRYL443 is part of the receptor-binding domain (RBD) of the spike protein of SARS-CoV. Peptide libraries were screened by surface plasmon resonance (SPR) to identify RBD binding epitopes. 438YKYRYL443 carries the dominant binding epitope and binds to ACE2 with KD=46μM. The binding mode was further characterized by saturation transfer difference (STD) NMR spectroscopy and molecular dynamic simulations. Based on this information the peptide can be used as lead structure to design potential entry inhibitors against SARS-CoV and related viruses.