Fig. 5. Quaternary packing of NTD and CTD.
a α-coronavirus S1 and δ-coronavirus S1 use intrasubunit packing pattern. NTD and CTD from the first monomer are colored blue, the second are colored red, and the third are colored magenta. PDB codes: HCoV-229E, 6U7H; PdCoV, 6B7N. b β-coronavirus S1 and γ-coronavirus S1 use cross-subunit packing pattern. NTD and CTD from the first monomer are colored blue, the second are colored red, and the third are colored magenta. The extra loop of IBV and the extra domains of β-CoVs are colored yellow and labeled as EX. PDB codes: MHV, 3JCL; IBV, 6CV0; SARS, 5XLR.