Spike Glycoprotein of SARS-CoV-2 Omicron Variant Lineages BA.4 and BA.5 (S protein (BA.4/BA.5))

The spike glycoprotein (S protein) is a trimeric surface protein of SARS-CoV-2 Omicron lineages BA.4 and BA.5. It is essential for viral entry into host cells by binding to the ACE2 receptor. BA.4/BA.5 variants possess numerous mutations in the S protein, particularly in the receptor-binding domain (RBD), leading to increased immune evasion and altered receptor binding affinity compared to earlier variants. The extensive glycosylation of the S protein further contributes to immune shielding. The S1 subunit contains the RBD, which binds ACE2, and the S2 subunit mediates membrane fusion. Proteolytic cleavage at the S1/S2 boundary and the S2' site are essential for activation. The protein exists in both "up" (RBD accessible) and "down" (RBD inaccessible) conformations.

Other names

SARS-CoV-2 Spike Protein (Omicron BA.4/BA.5)Spike proteinS glycoprotein

The S protein mediates viral entry by binding to ACE2, leading to membrane fusion. Some drugs aim to block this interaction or neutralize the protein to prevent infection.