Architecture of the SARS coronavirus prefusion spike

Abstract

The emergence in 2003 of a new coronavirus (CoV) responsible for the atypical pneumonia termed severe acute respiratory syndrome (SARS) was a stark reminder that hitherto unknown viruses have the potential to cross species barriers to become new human pathogens. Here we describe the SARS-CoV 'spike' structure determined by single-particle cryo-EM, along with the docked atomic structures of the receptor-binding domain and prefusion core.

Figure 1. Cryo-EM and three-dimensional reconstruction of SARS-CoV.

(a,b) Images at 8 μ (a) and 5.5 μ (b) defocus. S indicates spikes; arrowhead marks angle (θ) measured between two spikes. Inset shows envelope (E) and nucleocapsid (NC). (c,d) Select two-dimensional class averages from the defocus data in a and b, respectively. (e) Spike attached to the viral envelope by a narrow stalk. (f) Model of SARS-CoV with spikes spaced isotropically at 23.8°, surface-sectioned to reveal the interior. Orange, spike; green, stalk; blue and pink, envelope bilayer; red, nucleocapsid.

Figure 2. Fitting atomic-resolution structures within the spike.

(a,b) Putative locations of the fusion peptide and receptor-binding domain in the SARS spike (a) and influenza HA (b; PDB entry 1HA0), shown at the same resolution, colored according to cylindrical depth. (c) The SARS spike in side and end-on views, with the docked heptad-repeat prefusion core (PDB entry 2FXP⁶) and receptor-binding domain (PDB entry 2AJF⁷) bound to ACE-2.