SARS-CoV-2 spike protein ectodomain (non-RBM epitopes) (SARS-CoV-2 S (non-RBM))

The SARS-CoV-2 spike (S) protein ectodomain outside the receptor-binding motif (RBM) encompasses several critical structural regions, including the N-terminal domain (NTD), the non-RBM portion of the receptor-binding domain (RBD), and the S2 subunit (UniProt P0DTC2). While the RBM is the primary site for binding the host ACE2 receptor, it is also the most frequent site for escape mutations; in contrast, the non-RBM regions often contain highly conserved epitopes across different variants of concern and even other sarbecoviruses (Nature, 2021, 597(7874):103-108). These regions are essential for the structural integrity of the spike trimer and the conformational changes required for membrane fusion (Science, 2020, 367(6483):1260-1263). Therapeutic strategies targeting these areas, such as broadly neutralizing antibodies like Sotrovimab, aim to provide protection against a wider range of viral variants by inhibiting steps like proteolytic cleavage or the transition to a post-fusion state (Nature, 2022, 603(7902):706-713). Additionally, the S2 subunit is particularly conserved and serves as a target for fusion inhibitors that prevent the formation of the six-helix bundle required for membrane merging (Science, 2021, 373(6559):1109-1116). Consequently, these epitopes are vital for the development of "variant-proof" vaccines and long-acting monoclonal antibody therapies that maintain efficacy despite viral evolution.

Other names

SARS-CoV-2 spike protein non-RBM regionsSARS-CoV-2 S2 subunitSARS-CoV-2 N-terminal domainConserved spike epitopesSARS-CoV-2 S protein ectodomain

Inhibition of viral entry through multiple mechanisms: blocking membrane fusion by targeting the S2 subunit, inducing steric hindrance that prevents ACE2 binding via non-RBM RBD epitopes, or stabilizing the pre-fusion conformation by binding the NTD (Nature, 2021; Science, 2020).