Influenza! There’s H1N1 (swine flu), H5N1 (avian flu), H2N2 (Asian flu), H3N2 (Hong Kong flu), and many more combinations of H’s and N’s with numbers. But what do they mean?
Influenza viruses can be identified by the chemical structures of specific proteins on the outer surface coat of the virus. The two main proteins found on influenza are Hemagglutinin (“H”) and Neuraminidase (“N”). There are more than 10 known forms of H and 9 versions of N. Different strains of influenza can be characterized by the type of H or N that they carry (H1N1, or H3N2, etc.).
The H protein allows the virus to stick to cells and gain entry so that the virus can be replicated. In a way, Hemagglutinin acts as a key that fits into the lock (protein receptor) on a cell membrane. If the key fits, the virus can enter the cell, release its RNA for reverse transcription, integrate viral DNA into the cell’s DNA, and create new viral proteins. If the key doesn’t fit, then the cell is safe from that particular strain of influenza.
The N protein, “neuraminidase”, is an enzyme that helps the virus escape from cells once new viral particles have been synthesized. This enzyme cleaves specialized sugar molecules that are often associated with the proteins found on the surface of cells (glycoproteins). N proteins are basically scissors, snipping the new viruses from the plasma membrane of the cell so they can infect new cells to continue replication.
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