How to get URL link on X (Twitter) App
https://twitter.com/TheMenacheryLab/status/1899800371272290622I've hypothesized previously that the answers to "why use an insertion" and "why use a leading proline" lie in MERS, whose S1/S2 loop is 4 AAs longer than that of SARS-like CoVs, and also has the leading proline, making it more exposed to proteases:
https://x.com/ydeigin/status/1782490749889552740
https://twitter.com/breakfast_dogs/status/1900331687768137900Somewhat counterintuitively, in a human coronavirus, OC43, when it has the less efficient (“suboptimal”) RRSR furin cleavage site instead of the canonical RRSRR one, it is more lethal and more *neurovirulent* when tested in a mouse model:
https://twitter.com/solidevidence/status/1872953895280169172First an aside on extrapolating insertions found in SARS2 circulating in humans to the likelihood of insertions occurring (and getting fixed) in a SARS2 progenitor circulating in an intermediate host — SARS2 has now been circulating for years in hundreds of millions of humans, while in the wild it could not have had even a sliver of such a reservoir of non-bat hosts (and we all agree the FCS insertion could not have arisen in bats because it is detrimental to their preferred enteric tropism).
https://twitter.com/ydeigin/status/1731399158479675632
https://twitter.com/ydeigin/status/1631785943916060672
https://twitter.com/R_H_Ebright/status/1629543155807965184Here is the 2017 paper in which they created 8 SARS-like chimeras:
https://twitter.com/OAlexanderDK/status/1624441197665087489The most recent such P8 flight before the Nord Stream explosions occurred overnight between Sep 25-25. It is actually interesting because if went off radar for 4+ hours between 20:36 and 01:13 (UTC). Here's its track: