Thread by @NavroopSingh_

SARS-CoV-2 and the Secret of the Furin Site
preprints.org/manuscript/202…

The SARS-CoV-2 high infectivity is due to the functional polybasic furin cleavage site in the S protein. How it was acquired is unknown. There are two challenges to face: (i) an evolutionary model, to fit the origin of the coronavirus; and (ii) a molecular mechanism for the site

Here we show genomic fingerprints which are specific of Pangolin-CoVs, Bat-SARS-like (CoVZC45, CoVZXC21), bat RatG13 and human SARS-CoV-2 coronaviruses.

This, along with phylogenetic analysis, we found that these species have the same evolutionary origin in the bat, including a genetic recombination of S gene between Pangolin-CoV (2017) and RatG13 ancestors.

However, this does not explain why SARS-CoV-2 is the only of them with the furin site, which consists in four amino acid (PRRA) motif. The Arginine doublet is encoded by CGGCGG codons.

Surprisingly, none of the Arginine doublet of other furin site of viral proteins from several type of viruses, are encoded by the CGGCGG codons.

Taken together, all these lines of evidence and reasoning show that the acquisition of the polybasic furin cleavage site by SARS-CoV-2 is a “missing link” in our understanding of its evolutionary history, that can only be addressed through the discovery of new viruses.

"Nothing in Biology Makes Sense Except in the Light of Evolution" becomes more relevant in the case of the pandemic virus, not only because there is the hypothesis of a laboratory origin, but also because there is a furin site that has changed the world.

This paper concludes that the Furin Cleavage Site of SARS CoV 2 at the junction of S1/S2 of its Spike Protein which makes it more infectious has mysterious origin & its the missing link in its evolutionary theory. Hinting at the lab leak theory !