Enhanced stability of the SARS CoV-2 spike glycoprotein following modification of an alanine cavity in the protein core

• DOI: 10.1371/journal.ppat.1010981
• Publication Date: 2023-05-18T17:59:20Z
• Authors: Pantelis Poumbourios; Christine Langer; Irene Boo; Tasnim Zakir; Rob J. Center; Anouschka Akerman; Vanessa Milogiann...; Anupriya Aggarwal; Bronte A. Johnstone; Jungmin Ha; Fasséli Coulibaly; Stuart G. Turville; Heidi E. Drummer
• Keywords: Coiled coil; Heptad repeat; Alanine; Trimer

The spike (S) glycoprotein of SARS CoV-2 is the target neutralizing antibodies (NAbs) that are crucial for vaccine effectiveness. S1 subunit binds ACE2 while S2 mediates virus-cell membrane fusion. a class I fusion and contains central coiled coil acts as scaffold conformational changes associated with function. unusual in 3-4 repeat inward-facing positions mostly occupied by polar residues mediate few inter-helical contacts prefusion trimer. We examined how insertion bulkier hydrophobic (Val, Leu, Ile, Phe) to fill cavity next Ala1016 Ala1020 affects stability antigenicity S trimers. Substitution context prefusion-stabilized trimer, S2P-FHA, was increased thermal stability. function retained Ala1016/Ala1020 cavity-filling mutations improved recombinant S2P-FHA thermostability, however 2 mutants, A1016L A1016V/A1020I, lacked ability entry S-HIV-1 pseudoparticles into 293-ACE2 cells. When assessed immunogens, two thermostable mutants derived from ancestral isolate, (16L) A1016V/A1020I (VI) elicited antibody 50%-inhibitory dilutions (ID50s) range 2,700-5,110 Delta-derived viruses, 210-1,744 Omicron BA.1. antigens specificities directed receptor-binding domain (RBD), N-terminal (NTD), peptide stem region S2. VI mutation enabled production intrinsically stable BA.1 BA.4/5 S2P-FHA-like ectodomain oligomers absence an external trimerization motif (T4 foldon), thus representing alternative approach stabilizing oligomeric vaccines.