Viral Architecture of SARS-CoV-2 with Post-Fusion Spike Revealed by Cryo-EM

Chuang Liu; Yang Yang; Yuanzhu Gao; Chenguang Shen; Bin Ju; Congcong Liu; Xian Tang; Jinli Wei; Xiaomin Ma; Weilong Liu; Shuman Xu; Yingxia Liu; Jing Yuan; Jing Wu; Zheng Liu; Zheng Zhang; Peiyi Wang; Lei Liu

Different with spikes reported in previous study [5] , spikes in our images are much thinner both in negative staining image ( Figure 2 ) or cryo-EM image ( Figure 3 ). Spikes here have nail-like shape with a long body embedded in the envelope. Width of spike's head is around 7 nm. The length of whole spike is around 23nm. S protein of coronavirus consisted of S1 and S2 subunits. When S1 subunit is disassociated, S2 undergoes a conformation change, extending itself from compressed form to a nail-like shape, termed as post-fusion state. The nail-like shape was also observed by other researchers [13] [14] [15] . Work done by Song et al. [15] gave a detailed structure analysis of S2 protein using recombinant protein. Not only they reported the morphology of S2 protein at post-fusion state, they also reconstructed a 3D map. The 2D average image ( Figure 2E ) and 3D map ( Figure 2D ) reported in their paper [15] , have a consistent result with our observation both in negative staining or Cryo-EM images (shown in Figure 2C and Figure 3E ,3F).