IAV H9N2 HA

Influenza A virus causes influenza in birds and some mammals, and is the only species of the Alphainfluenzavirus genus of the Orthomyxoviridae family of viruses.

Influenza A Virus H9N2 Hemagglutinin

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.

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 of about two third of the virus particles through clathrin-dependent endocytosis and about one third through a 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 cell Source: UniProtKB-UniRule
Fusion of virus membrane with host endosome membrane Source: UniProtKB-UniRule
Fusion of virus membrane with host plasma membrane Source: InterPro
Viral budding from plasma membrane Source: UniProtKB-UniRule
Virion attachment to host cell Source: UniProtKB-KW

Virion membrane; Host apical cell membrane. Abundantly expressed at the apical plasma membrane in infected polarized epithelial cells, in close proximity to budding and assembled virions. Minor component of virions (only 16-20 molecules/virion).

Extracellular: 19-526
Helical: 527-547
Cytoplasmic: 548-560

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.