PROS1 and severe acute respiratory syndrome: Furthermore, F26G18 and its chimera mapped to a discrete sequential epitope (460FSPDGKPCTPPALNCYW476), which overlaps the ACE2 binding site, in the RBD of SARS-CoV S protein,23 suggesting that F26G18 neutralizes SARS-CoV infection by blocking RBD-ACE2 the binding.