S Glycoproteins

S glycoproteins are located outside the virion and give the virion the typical shape. The S protein form  homotrimers, which allow the formation of sun-like morphologies that give the name of Coronavirus. S proteins bind to virion membrane via the C-terminal transmembrane regions and they also interact with M proteins. Virions can be bound  to specific surface receptors in the plasma membrane of the host cell via the N-terminus of the S proteins.