Hemagglutinin (HA) is an antigenic glycoprotein, which is placed on the surface of the influenza viruses. It is responsible for binding the virus to the host cell, that is being infected. The name „hemagglutinin“ comes from the ability of protein to cause erythrocytes to agglutinate („clump together“). The process is like this: Hemagglutinin (HA) binds to the monosaccharide sialic acid which is present on the surface of its target host cells. The cell membrane then engulfs the virus through endocytosis and followed by formation of endosome. The cell then attempts to begin digesting the contents of the endosome by acidifying its interior and transforming it into a lysosome. When the pH decrease to 6.0, the HA molecule becomes partially unfold, and release a hydrophobic portion of peptide chain that was previously hidden. This so-called „fusion peptide“ acts like a molecular grapple hook for lock on the endosomal membrane. The rest of the HA molecule refolds into a new structure and pulls the endosomal membrane right up next to the viral membrane, causing the two to fuse together. When it happened, the viral RNA genome enters into the cell‘s cytoplasm.

Central European Institute of Technology Brno University of Technology Czech Republic European Union

Department of Chemistry and Biochemistry Mendel University in Brno Czech Republic European Union