Severe acute respiratory syndrome coronavirus 2 Spike protein (Omicron lineage) (SARS-CoV-2 S protein (Omicron))

The SARS-CoV-2 Spike (S) protein of the Omicron lineage (B.1.1.529 and its descendants) is a homotrimeric class I fusion glycoprotein that is essential for viral entry into human cells (UniProt P0DTC2). It is composed of the S1 subunit, which contains the receptor-binding domain (RBD) for attachment to the human angiotensin-converting enzyme 2 (ACE2) receptor, and the S2 subunit, which mediates the fusion of the viral and host cell membranes (Cui et al., 2022, Nature). The Omicron lineage is distinguished by a high density of mutations—over 30 in the Spike protein alone—which enhance ACE2 binding affinity and facilitate significant escape from neutralizing antibodies produced by prior infections or early-generation vaccines (Cao et al., 2022, Nature). This protein serves as the primary immunogen in most COVID-19 vaccines and the target for therapeutic monoclonal antibodies. Due to its rapid evolution, the Omicron Spike protein presents a moving target for drug development, requiring the design of more conserved epitope-targeting agents and bivalent vaccine formulations (Hoffmann et al., 2022, Cell). Understanding the structural dynamics of the Omicron Spike is crucial for predicting future variants and developing pan-coronavirus countermeasures (NIH, 2023).

Other names

Spike glycoproteinS proteinB.1.1.529 Spike proteinOmicron S proteinSurface glycoprotein

Monoclonal antibodies and vaccine-induced antibodies bind to specific epitopes on the Spike protein, particularly the receptor-binding domain (RBD), to sterically hinder the interaction with the host ACE2 receptor or prevent the conformational changes necessary for viral-host membrane fusion (Hoffmann et al., 2022, Cell).