General information on Spike protein
Spike protein is a structure located in the virus coat also known as capsids. These transmembrane structures are thought to have unusually high strength and stiffness. As such, viral spike proteins are involved in broaching the membrane of the target cell and provide a pathway for the virus to conduct its nucleic acid into the target cell. Viral spike protein consists of several repeats of short assembled β-strand sheets stabilized by hydrogen bonds. Once assembled, spike protein form trimer structures on the surface of the virus which gives the virus a crown-like shape or ‘corona’ shape. However, higher order structure may vary significantly from one virus type to another.
Spike protein has been reported to be involved in the mechanism that lead to virus entrance in the cell. This is the case for the coronavirus responsible for coronavirus disease 2019 (COVID-19). COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which affects respiratory epithelial cells. SARS-CoV-2 spike protein binds to angiotensin converting enzyme 2 (ACE2) and CD209L protein which lead to COVID virus to enter the target cell via endocytosis. Two domains, namely S1 and S2, are responsible for the binding step. S1 domain is involved in host cell receptor recognition and binding. Once S1 domain binds the receptor, it results in a conformational change of the S2 domain which facilitates the fusion between viral envelope and the plasma membrane of its target cell. S2 domain contain the putative fusion peptide as well as heptad repeat HR1 and HR2.
Antibody binding on the N-terminal of SARS spike protein can inhibit its activity and blocks the infection as a result. Furthermore, spike protein is the target of CD4 and CD8 immune cells. For these reasons, SARS spike protein is considered as a potential target for the neutralization of SARS virus.
We can provide several fragments for COVID spike protein including:
As well as the peptide fragments such as:
or subunits (S1)