Hemagglutinin (HA) is an antigenic glycoprotein found on the surface of the Influenza virus and is responsible for binding the virus to the cell that is being infected.

Subtypes

Thirteen hemagglutinin subtypes are known.

Function

Hemagglutinin binds to a sialic acid residue on the cell to be infected. The name derives from the protein's ability to adhere to red blood cells and causes them to agglutinate, or stick together.

Structure

The HA monomer is synthesized as a precursor and it is glycosylated then cleaved into two smaller proteins: The HA1 and HA2 subunits. Each HA monomer consists of a long, helical chain anchored in the membrane by HA2 and topped by a large HA1 globule.

See also

• Neuraminidase