Here’s one more excerpt from our guide to COVID-19 Genes & SNPs, that focuses on the FURIN gene
- Furin is an enzyme encoded by the FURIN gene. Furin is a proprotein convertase and acts to cleave sections of inactive proteins, in order to activate them. The Furin enzyme is highly expressed in lungs.
- NOTE: Proprotein convertases are a family of nine serine secretory proteases proteins that activate other proteins. Many proteins are inactive when they are first synthesized, because they contain chains of amino acids that block their activity. Proprotein convertases remove those chains and activate the protein.
- The proprotein convertase family is responsible for the activation of a wide variety of precursor proteins, such as growth factors, hormones, receptors and adhesion molecules, as well as cell surface glycoproteins of infectious viruses
- In addition to processing cellular precursor proteins, Furin is also utilized by a number of pathogens. For example, the envelope proteins of viruses influenza, HIV, SARS-CoV-2 and several filoviruses including Ebola Marburg virus must be cleaved by furin or furin-like proteases to become fully functional and active.
- As previously discussed, the spikes “crowning” the SARS-CoV-2 must attach (AGT2), fuse (TMPRSS2) and gain entry to cells.
- David Veesler, senior author of the report referenced below and assistant professor of biochemistry at the UW School of Medicine, said that “The spike is the business part as far as viral entry. It is in charge not only of attachment at the host cell surface, but also of fusing the viral and host cell membranes to allow the infection to start.”
- He goes on to say that, “…unlike SARS-CoV, SARS-CoV-2 includes a furin cleavage site at a boundary between two subunits of the spike protein. It is not yet known if this difference is expanding the kinds of cells the SARS-CoV-2 could infect or enhancing its transmissibility, in a way that might be similar to that of highly pathogenic avian flu viruses.”
- Thus, when SARS-CoV-2 attaches to ACE2 cell surface receptors in the respiratory tract, it may then successfully exploit this Furin enzyme to activate its own surface glycoprotein to gain entry to respiratory tract cells. This makes SARS-CoV-2 a very easily transmittable virus. This was not the case with 2002-2003 SARS-CoV.
- Binds 3 calcium ions per subunit
- Optimum pH is 6.0