The hemagglutinin HA1 protein is essential for attachment of virions to host cells by binding to sialic acid-containing receptors, inducing virion internalization via clathrin-dependent or clathrin- and caveolin-independent pathways.As a class I viral fusion protein, HA1 determines host range restriction and virulence, mediating fusion between the virion membrane and the endosomal membrane.HA/Hemagglutinin Protein, H5N9 (ABR37720, sf9, His) is the recombinant Virus-derived HA/Hemagglutinin protein, expressed by Sf9 insect cells , with C-His labeled tag.
