Fig. 3: Structural comparison of HCoV-229E spike S2 subunit in different conformaitons reveals closed-to-open conformational changes.

a Overall structural comparison of the S2 subunit from C1, C2, and the previously reported open HCoV-229E S protein (PDB ID: 6U7H). b Zoomed-in comparison of CH. The CH is twisted outward relatively to the symmetry axis gradually from C1 to C2 to open HCoV-229E S protein with twister angles of −78°, −78.2° and −86°, respectively. c Close-up views of HR1. The Phe in helix (residues Gln791-Phe809) of C2 goes upward 7 Å compared to that of C1. The helix (residues Gln821-Arg852) of open HCoV-229E S protein rotates outward by 15° Compared to that of C1 (similar to C2). d Structural comparison of FP. The FP of C2 goes upward 4.5 Å relatively with that of C1 and can be further exposed with a clockwise rotation of about 10° from C1 to the open HCoV-229E S protein. C1 and the previously reported open S protein (PDB ID: 6U7H) are colored in gray and dark gray, respectively. The C2 is colored as Fig. 1a. Some loops between the secondary structures are omitted for clarification.