SARS-CoV-2 spike protein S1 subunit (S1)

The SARS-CoV-2 spike (S) protein is a large trimeric class I fusion glycoprotein that mediates viral entry into host cells. It is proteolytically cleaved by host proteases into two distinct subunits: S1, which handles receptor binding, and S2, which facilitates membrane fusion. The S1 domain contains the N-terminal domain (NTD) and the receptor-binding domain (RBD), the latter of which specifically interacts with the human angiotensin-converting enzyme 2 (ACE2) receptor to initiate infection. This interaction is a primary determinant of viral host range and tissue tropism. As the most exposed part of the virus, the S1 domain is the principal target for neutralizing antibodies and the majority of COVID-19 vaccines. However, the S1 domain is highly mutable, particularly within the RBD, which allows the virus to evolve and escape existing immunity through antigenic drift. Beyond its role in acute infection, the S1 subunit has been implicated in the pathogenesis of Long COVID through its ability to induce pro-inflammatory responses and endothelial dysfunction independent of viral replication.

Other names

SARS-CoV-2 spike protein S1 domainSARS-CoV-2 S1Spike protein S1 subunitSurface glycoprotein S1 subunit2019-nCoV S1 protein

Neutralization of viral entry by binding to the S1 subunit (specifically the RBD) and blocking its interaction with the host ACE2 receptor.