Best Posts in Thread: Interesting Interview about Vaccine's and Covid Origin

Explanation of Furin Cleavage site referred to in the above video



Viruses rely on the biochemical mechanisms of the host cell they invade to bind and fuse with the host cell membrane and replicate inside the cell.

The fusion part of that cascade of events can involve the virus using host cell enzymes to cleave one or more of the virus’ proteins at specific sites to facilitate entry into the host cell.




Those sites are often composed of relatively short sequences of chemically basic amino acids called polybasic cleavage sites.

At the junction of the S1 and S2 protein subunits, COVID-19 has just such a polybasic cleavage site that uses the host cell enzyme furin, which is found in many human organ systems and known to be involved in the pathogenic processes of viruses, for example, HIV, Ebola and various strains of coronavirus.

The presence of the furin polybasic cleavage site may explain clinical reports of COVID-19’s ability to infect a variety of organ systems.

The furin polybasic cleavage site in COVID-19 can be roughly defined by the amino acid sequence SPRRARS, which is Serine-Proline-Arginine-Arginine-Alanine-Arginine-Serine, where the cleavage takes place at the R-S junction.

Within that broader sequence, the minimum sequence for a furin cleavage site is R-X-X-R, where Arginine (R) occurs in the 3rd and 6th positions and positions 4 and 5 can be any amino acid, but activity of the furin cleavage site can be significantly enhanced with a basic amino acid like Arginine in the 4th position, as occurs in COVID-19.

It is very important to note that the furin polybasic cleavage site in COVID-19 is unique and has not been found in any of the coronaviruses yet identified as close relatives.

 

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