Coronavirus Spike Protein (MERS-CoV S1; 56-295)

MERS-CoV spike protein plays an important role in virus binding and entry, and the development of MERS-CoV entry/fusion inhibitors targeting the S1 subunit, particularly the receptor-binding domain, and the S2 subunit, especially the HR1 region, of the MERS-CoV spike protein. Spike glycoprotein cleaved into three chains: S1, S2’ and S2. S1 attaches the virion to the cell membrane by interacting with host receptor, initiating the infection. S2’ acts as a viral fusion peptide which is unmasked following S2 cleavage occurring upon virus endocytosis. S2 mediates fusion of the virion and cellular membranes by acting as a class I viral fusion protein. Under the current model, the protein has at least three conformational states: pre-fusion native state, pre-hairpin intermediate state, and post-fusion hairpin state. During viral and target cell membrane fusion, the coiled coil regions (heptad repeats) assume a trimer-of-hairpins structure, positioning the fusion peptide in close proximity to the C-terminal region of the ectodomain. The formation of this structure appears to drive apposition and subsequent fusion of viral and target cell membranes.