Fig. 1

Open/closed state of ACE2 and S-protein binding. a Closed state when ACE2 binds MLN-4760 (XX5) inhibitor (PDB1r4l). b Open/native state of ACE2 (PDB 1r42). c Most PDB structures show that SARS S-protein (colored yellow) binds the open state of ACE2, as from one monomer of PDB 3scl. d S-protein shows binding to closed state of ACE2 from another monomer of PDB 3scl