H1N1 HA1 (A/California/04/2009) His Tag

Neuraminidase (NA)and hemagglutinin (HA) are major membrane glycoproteins found on the surface ofinfluenza virus. Hemagglutinin binds to the sialic acid-containing receptors onthe surface of host cells during initial infection and at the end of aninfectious cycle. Hemagglutinin also plays a major role in the determination ofhost range restriction and virulence. As a class I viral fusion protein,hemagglutinin is responsible for penetration of the virus into the cellcytoplasm by mediating the fusion of the membrane of the endocytosed virusparticle with the endosomal membrane. Binds to sialic acid-containing receptorson the cell surface, bringing about the attachment of the virus particle to thecell. This attachment induces virion internalization either throughclathrin-dependent endocytosis or through clathrin- and caveolin-independentpathway. Plays a major role in the determination of host range restriction andvirulence. Class I viral fusion protein. Responsible for penetration of thevirus into the cell cytoplasm by mediating the fusion of the membrane of theendocytosed virus particle with the endosomal membrane. Low pH in endosomesinduces an irreversible conformational change in HA2, releasing the fusionhydrophobic peptide. Several trimers are required to form a competent fusionpore.