Severe acute respiratory syndrome coronavirus 2 spike protein receptor-binding domain (SARS-CoV-2 spike RBD) (SARS-CoV-2 RBD)

The Severe acute respiratory syndrome coronavirus 2 spike protein receptor-binding domain (SARS-CoV-2 spike RBD) is a critical subunit within the S1 portion of the viral spike glycoprotein, responsible for mediating initial attachment to host cells by binding angiotensin-converting enzyme 2 (ACE2). Located at residues approximately 319-541, this domain undergoes dynamic conformational changes, including transitions between closed and open states, κ-helix and β-strand structures, and hinge movements that expose binding motifs for receptor engagement. These motions facilitate viral entry by promoting membrane fusion through the adjacent S2 subunit after cleavage events at S1/S2 and S2' sites. In COVID-19 pathogenesis, the RBD's high affinity for ACE2 drives efficient infection of respiratory epithelial cells, contributing to viral transmission and disease severity. Therapeutic strategies target the RBD extensively, including neutralizing monoclonal antibodies (e.g., those binding the ACE2 interface), soluble RBD decoys that competitively inhibit viral attachment, and stabilized RBD variants used in vaccines to elicit protective immunity without shifting to post-fusion forms. Structural features like a linoleic acid-binding cavity and conserved disulfide bonds in the hinge region pose challenges for stability and drug design, but also offer opportunities for allosteric inhibition. Overall, the RBD remains a prime antiviral target due to its essential role in entry, though viral evolution introduces variants that alter binding and escape immunity.

Other names

SARS-CoV-2 spike RBDSARS2-RBDReceptor-binding domain (RBD) of SARS-CoV-2 spike protein

Competitive inhibition of ACE2 binding (e.g., soluble RBD decoys); Neutralization by antibodies blocking RBD-ACE2 interaction; Stabilization of prefusion conformation to prevent entry