It’s time to answer one of the main questions regarding the abnormalities of the neo-discovered sarbecovirus: What a furin cleavage site is?
Unlike other coronaviruses, which are much less dangerous, Sars-CoV-2 has a small, extra, sequence located on the side of the spike protein (the small hook that binds to ACE2 receptors on the outer surface of human cells). This “extra piece” is cut by the cellular enzyme furin through hydrolysis. Thanks to this cut, the Spike can bind to a second receptor, Neuropilin-1, facilitating entry into the human cell and making SARS-CoV-2 the terrible virus we know.
Where does a furin cleavage site come from? Does it normally form in nature? Maybe.
It is possible to develop it both naturally and artificially, but, as emerged in the revised study by Rossana Segreto and Yuri Deigin, both Drastic members, there are several suspicious elements. The other known natural betacoronaviruses do not have a furin cleavage site, furthermore, in SARS‐CoV‐2 it does not appear to be in frame with the rest of the sequence when compared with the sequences of MP789 (pangolin coronavirus) and RaTG13 (the most closely related known virus).
Therefore, it is possible to exclude that such insertion could have originated from polymerase slippage or from releasing and repriming, since insertion mutations generated by these mechanisms have been postulated to maintain the reading frame of the viral sequence. The possibility that the furin cleavage site may have been acquired by recombination has recently been questioned by Seyran et al. 3 because the SARS‐CoV‐2 spike protein appears to lack further recombination events in contrast to the pattern of recombination of other coronaviruses.
Furthermore, we know that the only lineage B coronavirus having a furin cleavage site that officially appeared on earth prior to SARS-CoV-2 is a SARS-related genetically engineered from Follis et al. 4.
All this series of suspicious genetic elements combined with the abnormal amount of strange coincidences on many other fronts presented on this website must strongly push international opinion to investigate as far as possible a laboratory origin of the SARS-CoV-2 virus.