Cryo-EM structure of the SARS coronavirus spike glycoprotein in complex with its host cell receptor ACE2
Fig 2
Structural comparisons of the ACE2-bound and ACE2-free SARS-CoV spikes.
(A) Schematic and topology diagrams showing the domain organization. NTD, CTD3 and S2 are colored grey, CTD1 is colored red, CTD2 is colored orange, CTD1-CTD2 linkers are colored blue. (B) Cross-correlation coefficients (CCs) between the CTD2s or the S2s of different conformations. *Values in the parentheses are the CCs between the S2s of different conformations. Density maps were low-pass filtered to 5.5 Å and were compared at a contouring level of 4.0 σ. (C) Ribbon-diagram structural comparisons of the ACE2-bound conformation 3 and the unbound-down conformation. ACE2, CTD1, CTD2, CTD3 and S2 of the ACE2-bound conformation 3 are colored green, red, yellow, pink and pink respectively. The unbound-down conformation is colored grey. CTD2 and S2 domain are zoomed in to show the receptor-binding induced hinge motion of CTD2. (D) EM densities and corresponding atomic models represented in ribbon diagrams around the S2’ protease cleavage site: unbound-down conformation (left) and ACE2-bound conformation (right). The S2’ site is colored red and position of the S2’ site is indicated with black arrows. The fusion peptide is colored cyan. The “C” shape loop covering the S2’ site is colored blue.