Hemagglutinin protein, H1 subtype (H1)

The Hemagglutinin protein, H1 subtype (H1) is a trimeric glycoprotein on the surface of influenza A viruses, forming elongated spikes that project from the viral envelope. It consists of HA1 and HA2 subunits linked by disulfide bonds after proteolytic cleavage of the HA0 precursor, with a membrane-distal globular head domain primarily from HA1 responsible for binding sialic acid receptors on host cells, and a membrane-proximal stem domain involving both HA1 and HA2 that mediates low-pH-induced membrane fusion during viral entry. The receptor-binding subdomain in the head recognizes sialylated glycans, enabling viral attachment, while the fusion peptide at the N-terminus of HA2 drives endosomal-viral membrane fusion after conformational changes triggered by acidic conditions. H1 belongs to group 1 hemagglutinins, characterized by specific structural features like the interhelical loop in the fusion subdomain influencing subdomain orientations. In disease, H1 is central to influenza infections, including pandemics like 1918 and 2009, as the primary antigen eliciting neutralizing antibodies and driving viral evolution through antigenic drift and shift. Antigenic sites surround the receptor-binding pocket, with glycosylation modulating immune evasion. While not a direct small-molecule drug target, H1 is key for vaccine design, with monoclonal antibodies targeting conserved stem epitopes showing broad potential against diverse strains.

Other names

HAH1 hemagglutininInfluenza A virus hemagglutinin H1