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Influenza Hemagglutinin (HA) Protein Function

Q1: What's the function of Hemagglutinin (HA)?

Hemagglutinin (HA) or Haemagglutinin (BE) is an antigenic glycoprotein found on the surface of the influenza viruses. It is responsible for binding the virus to the cell that is being infected. The name "hemagglutinin" comes from the protein's ability to cause red blood cells (erythrocytes) to clump together ("agglutinate") in vitro. 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 forms 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 within the endosome drops to 6.0, the HA molecule becomes partially unfold, and releasing a very hydrophobic portion of its peptide chain that was previously hidden within the protein. This so-called "fusion peptide" acts like a molecular grappling hook by inserting itself into the endosomal membrane and locking on. Then, when the rest of the HA molecule refolds into a new structure and pulls the endosomal membrane right up next to the virus particle's own membrane, causing the two to fuse together. Once this has happened, the viral RNA genome enters into the cell's cytoplasm.


Q2: What's the function of Neuraminidase (NA)?

The main function of the Neuraminidase (NA) might be to remove receptors for influenza virus from newly formed virus particles so allowing these to be released and spread the infection. Another function of flu virus neuraminidase might be to destroy sialic acid containing inhibitors for the virus in the mucous secretions of the respiratory tract, so enabling the virus to more easily infect cells, and there may be other functions as yet undiscovered.


Q3: Potential functions of the stem domain of Hemagglutinin (HA)?

Studies have revealed that the stem N-glycans of HA is crucial for virus replication. In both culture systems, growth of virus lacking this glycans was completely blocked at 37 °C and inhibited at 33 °C. It is concluded that the stem N-glycans is indispensable for the formation of replication-competent influenza viruses.


Q4: How about antibody binding with the cap domain?

Antibody that binds to the cap region of the Hemagglutinin (HA) protein can possibly block the binding of the virus to the sialic acid, and hence could potentially prevent virus infection, or have neutralizing activity. Antibody raised from vaccination of hemagglutinin antigen can protect vaccinee from virus infection.



Influenza Research Reagents (Hot!)

Influenza virus antigen protein
Product Name Cat No.
Influenza H1N1 (A/California/07/2009) Hemagglutinin 11085-V08H
Influenza H1N1 (A/Puerto Rico/8/1934) Hemagglutinin 11684-V08H
Influenza H1N1 (A/California/04/2009) Hemagglutinin 11055-V08H
Influenza H1N1 (A/California/04/2009) Hemagglutinin 11055-V08B
Influenza H3N2 (A/Aichi/2/1968) Hemagglutinin 11707-V08H
Influenza H3N2 (A/Brisbane/10/2007) Hemagglutinin 11056-V08H
Influenza H5N1 (A/Anhui/1/2005) Hemagglutinin 11048-V08H1
Influenza H3N2 Virus Hemagglutinin Protein 40043-V08H
Influenza H7N9 (A/Anhui/1/2013) Hemagglutinin Protein 40103-V08B
Influenza H1N1 (A/Brisbane/59/2007) Hemagglutinin 11052-V08H
Influenza H5N1 (A/VietNeuraminidasem/1194/2004) Hemagglutinin 11062-V08H1
Influenza H7N9 (A/Anhui/1/2013) Hemagglutinin Protein 40103-V08H
Influenza H5N1 (A/Anhui/1/2005) Hemagglutinin 11048-V08H4
Influenza H1N1 (A/California/07/2009) Hemagglutinin Protein 11085-V08B
Influenza H1N1 Nucleoprotein Protein 11675-V08B
Influenza H1N1 (A/California/07/09) Nucleoprotein Protein 40205-V08B
Influenza H1N1 (A/California/04/2009 )Neuraminidase Protein (Active) 11058-V07B
Influenza H5N1 Neuraminidase (Active) 11676-VNAHC
Influenza H5N1 (A/Hubei/2011) Neuraminidase Protein (Active) 40018-V07H
Influenza H1N1 (A/Puerto Rico/8/34/Mount SiNeuraminidasei) Matrix Protein 1 40010-V07E
Influenza virus antigen antibody
Product Name Cat No.
Influenza H1N1 (Swine Flu 2009) Hemagglutinindy Antibo 11055-MM01
Influenza H1N1 (Swine Flu 2009) Hemagglutinin Antibody 11055-RM05
Influenza H7N9 Hemagglutinin Antibody, Rabbit Pab 40103-RP02
Influenza H1N1 (Swine) Hemagglutinin Antibody 11055-MM09
Influenza H1N1 Hemagglutinin Antibody 11684-RP01
Influenza H1N1 (Swine Flu 2009) Hemagglutinin Antibody 11055-RP02
Influenza H5N1 (Avian Flu) Hemagglutinin Antibody 11048-MM01
Influenza Virus Hemagglutinin Antibody, Rabbit MAb 86001-RM01
Influenza H3N2 Hemagglutinin Antibody 11056-MM03
Influenza H1N1 (Swine Flu 2009) Neuraminidase Antibody 11058-R001