Influenza A Hemagglutinin H1

Influenza A Hemagglutinin H1

Binds to sialic acid-containing receptors on the cell surface, bringing about the attachment of the virus particle to the cell. This attachment induces virion internalization either through clathrin-dependent endocytosis or through clathrin- and caveolin-independent pathway. Plays a major role in the determination of host range restriction and virulence. Class I viral fusion protein. Responsible for penetration of the virus into the cell cytoplasm by mediating the fusion of the membrane of the endocytosed virus particle with the endosomal membrane. Low pH in endosomes induces an irreversible conformational change in HA2, releasing the fusion hydrophobic peptide. Several trimers are required to form a competent fusion pore.

Clathrin-dependent endocytosis of virus by host cellIEA:UniProtKB-UniRule
Fusion of virus membrane with host endosome membraneIEA:UniProtKB-UniRule
Fusion of virus membrane with host plasma membraneIEA:InterPro
Viral budding from plasma membraneManual Assertion Based On ExperimentIDA:UniProtKB
Virion attachment to host cellIEA:UniProtKB-KW

Virion membrane; Host apical cell membrane. Targeted to the apical plasma membrane in epithelial polarized cells through a signal present in the transmembrane domain. Associated with glycosphingolipid- and cholesterol-enriched detergent-resistant lipid rafts.

Extracellular: 18-528
Helical: 529-549
Cytoplasmic: 550-565

Palmitoylated.
In natural infection, inactive HA is matured into HA1 and HA2 outside the cell by one or more trypsin-like, arginine-specific endoprotease secreted by the bronchial epithelial cells. One identified protease that may be involved in this process is secreted in lungs by Clara cells.