Severe acute respiratory syndrome coronavirus spike glycoprotein receptor-binding domain (Spike RBD (occasionally referred to as S RBD))

The **spike glycoprotein receptor-binding domain** (RBD) is a discrete region within the S1 subunit of the spike (S) glycoprotein of SARS-CoV and SARS-CoV-2, responsible for specifically recognizing and binding to the host cell receptor **angiotensin-converting enzyme 2 (ACE2)**[2][5][6][7]. The RBD is critical for viral attachment, mediating the first step of viral entry into host cells. Structurally, it is a portion of the S1 subunit (residues ~319–541 in SARS-CoV-2), adopting a unique fold that creates a receptor-binding motif (RBM) directly interacting with ACE2[6][7]. The RBD is the primary target for neutralizing antibodies and forms the basis for most COVID-19 vaccines and therapeutic antibodies[5][6][7]. Variations in the amino-acid sequence of the RBD underlie differences in infectivity, host range, and immune escape among viral strains. The domain is N-glycosylated and exhibits structural flexibility, facilitating immune evasion and receptor engagement[1][2]. Blocking the interaction of the spike RBD with ACE2 is the principal mechanism of action for all neutralizing antibody therapeutics and is a key focus of antiviral drug and vaccine development for both SARS and COVID-19[4][5][6][7].

Other names

Spike glycoprotein receptor-binding domainSpike RBDS protein RBDSARS-CoV-2 spike RBDSARS-CoV spike RBDS1-CTD (C-terminal domain of S1, also called RBD)[2]SARS-CoV-2 S RBD

Blockade of RBD-ACE2 interaction to prevent viral entry. Neutralization by antibody binding to RBD, inhibiting attachment or inducing S1 shedding. Inhibition of conformational change necessary for membrane fusion (for fusion inhibitors). Induction of adaptive immune response (for vaccines targeting RBD).