Structure and function of the spike glycoprotein of coronaviruses

The S glycoprotein of coronaviruses is a large,type I membrane glycoprotein that contains distinct func-tional domains near the amino(S1)and carboxyl(S2)termini.Trimers of the S glycoprotein form the characteristic spikes that protrude from the virion membrane.The S glycoproteins of coronaviruses have both receptor binding and membrane-fusing activities.The S1domain is responsible for viral attachment to specific host cell receptors and is the basis of coronaviruses' narrow host range specificity.The S2domain that contains the fusion peptide in its N-terminus is critical for the virion-cell fusion.On binding to its specific receptor,the S glycoprotein undergoes con-formational changes that exposes a hydrophobic fusion peptide which mediates fusion of the viral envelope with host cell membranes,releasing the viral nucleocapsid into the cytoplasm.The relationship of the S glycoprotein of coron-aviruses and cell receptors and membrane fusion is reviewed here.Finally,the structural characteristics of the SARS-CoV is introduced.