Hemagglutinin esterase

Hemagglutinin esterase (HEs) is a glycoprotein that certain enveloped viruses possess and use as invading mechanism. HEs helps in the attachment and destruction of certain sialic acid receptors that are found on the host cell surface. Viruses that possess HEs include influenza C, Toro-viruses, and coronaviruses. HEs is a dimer transmembrane protein consisting of two monomers, each monomer is made of three domains. The three domains are: membrane fusion, esterase, and receptor binding domains. Hemagglutinin esterase (HEs) is a glycoprotein that certain enveloped viruses possess and use as invading mechanism. HEs helps in the attachment and destruction of certain sialic acid receptors that are found on the host cell surface. Viruses that possess HEs include influenza C, Toro-viruses, and coronaviruses. HEs is a dimer transmembrane protein consisting of two monomers, each monomer is made of three domains. The three domains are: membrane fusion, esterase, and receptor binding domains. The different HEs enzyme activities include: receptor binding activity, receptor hydrolysis (esterase) activity, and membrane fusion activity. The receptor binding activity involve the attachment of HEs to N-acetyl-9-O-acetylneuraminic acid (9-O-Ac- Neu5Ac) of glycolipids and glycoproteins and in turn serve as viral receptor. Receptor hydrolysis (esterase) activity allows virus particles to escape the infected cell by removing an acetyl group from the C9 position of terminal 9-O-Ac-Neu5Ac residues. Membrane fusion activity helps in incorporation viral genome into the host cell cytoplasm by enhancing the attachment between the viral envelope and host cell membrane. In certain Influenza virus, the cell surface consists of both Hemagglutinin (HA) and Neuraminidase (NA) proteins that encompass enzymatic activities, whereas hemagglutinin-esterase fusion (HEF) proteins have been found to be the primary single spike protein that combines all of the enzymatic activities listed above. HEF proteins have been tested to be high-temperature and low-pH resistant and are the primary source of virulence in viruses.Influzena C have been shown to have unique HEF structure proteins that enhance its ability to infect the host cell compared to Influence A and B.