1918 Hemagglutinin

Influenza hemagglutinin (HA) is a glycoprotein found on the surface of influenza viruses. It is responsible for binding the virus to cells with sialic acid on the membranes, such as cells in the upper respiratory tract or erythrocytes. It is also responsible for the fusion of the viral envelope with the endosome membrane, after the pH has been reduced. The name "hemagglutinin" comes from the protein's ability to cause red blood cells (erythrocytes) to clump together ("agglutinate") in vitro. This particular model is of H1 Hemagglutinin from the 1918 influenza virus.