Comparison of the pre-fusion (orange, light blue) and post-fusion (red, dark blue) conformations of the SARS-CoV spike protein trimer. In the pre-fusion conformation, the central helix (orange) and heptad repeat 1 (HR1, light blue) are folded back on each other in an antiparallel orientation. In the post-fusion conformation, the central helix (red) and the HR1 sequence (dark blue) reorganize to form an extended trimeric coiled coil. The viral membrane is at the bottom and the host cell membrane at the top. Only key portions of the S2 subunit are shown. Rendered using PyMol from cryo-electron microscopy structures PDB: 6NB6​ (pre-fusion) and PDB: 6M3W​ (post-fusion) superposed using the central helix sequences, inspired by Figs 1 and 2 from Fan 2020.

6NB6: Unexpected Receptor Functional Mimicry Elucidates Activation of Coronavirus Fusion. Walls, A.C., Xiong, X., Park, Y.J., Tortorici, M.A., Snijder, J., Quispe, J., Cameroni, E., Gopal, R., Dai, M., Lanzavecchia, A., Zambon, M., Rey, F.A., Corti, D., Veesler, D. (2019) Cell 176: 1026-1039.e15

PubMed: 30712865 DOI: 10.1016/j.cell.2018.12.028

6M3W: Cryo-EM analysis of the post-fusion structure of the SARS-CoV spike glycoprotein. Fan, X., Cao, D., Kong, L., Zhang, X. (2020) Nat Commun 11: 3618-3618