Hemagglutinin (influenza)
Influenza hemagglutinin (HA) or haemagglutinin[p] (British English) is a homotrimeric glycoprotein found on the surface of influenza viruses and is integral to its infectivity.
| Hemagglutinin | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | Hemagglutinin | ||||||||
| Pfam | PF00509 | ||||||||
| InterPro | IPR001364 | ||||||||
| SCOP2 | 1hgd / SCOPe / SUPFAM | ||||||||
| OPM superfamily | 109 | ||||||||
| OPM protein | 6hjq | ||||||||
| |||||||||
| Influenza C hemagglutinin stalk | |||||||||
|---|---|---|---|---|---|---|---|---|---|
x-ray structure of the haemagglutinin-esterase-fusion glycoprotein of influenza c virus | |||||||||
| Identifiers | |||||||||
| Symbol | Hema_stalk | ||||||||
| Pfam | PF08720 | ||||||||
| InterPro | IPR014831 | ||||||||
| SCOP2 | 1flc / SCOPe / SUPFAM | ||||||||
| OPM superfamily | 277 | ||||||||
| OPM protein | 2jrd | ||||||||
| |||||||||
Hemagglutinin is a Class I Fusion Protein, having multifunctional activity as both an attachment factor and membrane fusion protein. Therefore, HA is responsible for binding Influenza virus to sialic acid on the surface of target cells, such as cells in the upper respiratory tract or erythrocytes, causing as a result the internalization of the virus. Secondarily, HA is responsible for the fusion of the viral envelope with the late endosomal membrane once exposed to low pH (5.0-5.5).
The name "hemagglutinin" comes from the protein's ability to cause red blood cells (erythrocytes) to clump together ("agglutinate") in vitro.