page_title: Hemagglutinin esterase
hierarchical_section_title: Hemagglutinin esterase
caption_attribution_description: বাংলা: 1flc কোডসহ নিবন্ধিত প্রোটিনের আণবিক গঠনের কার্টুন উপস্থাপনা। English: Cartoon representation of the molecular structure of protein registered with 1flc code. Deutsch: Grafik des Molekularstruktur von jenem Protein, das mit 1flc code registriert ist. Plattdüütsch: Grafik, de de Molekularstruktur von dat Protein wiest, dat mit’n Kood 1flc registreert is.
context_page_description: Hemagglutinin esterase 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 virus, toroviruses, 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 activity, and membrane fusion activity. The receptor binding activity involve the attachment of HEs to N-acetyl-9-O-acetylneuraminic acid of glycolipids and glycoproteins and in turn serve as viral receptor. Receptor hydrolysis 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.
context_section_description: 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 virus, toroviruses, and coronaviruses (but not SARS-like 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 viruses, 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. Influenza C have been shown to have unique HEF structure proteins that enhance its ability to infect the host cell compared to Influenza A and B.
  The folding of different domains in the hemagglutinin-esterase protein is important for intracellular transport of proteins from the endoplasmic reticulum to the Golgi apparatus. The presence of oligosaccharide chains in the E, F, and R domains of the HE enzyme also influence intracellular transport. Acylation of the hemagglutinin-esterase has shown to play an essential role in virus particle assembly replication. The exact process of enzyme catalytic cleavage has not yet been detailed out. However, proteolytic cleavage must occur before hemagglutinin-esterase membrane fusion activity. HEF proteins have a unique spikes hexagonal arrangement. This feature is unique to Influenza C virus particles. The arrangement is a covering outside of the particle.
caption: The structure of the Hemagglutinin Esterase protein.
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