Nature has an interesting piece regarding the aggressiveness of the Delta variant. They note:
other groups have zeroed in on a mutation that alters a single amino acid in the SARS-CoV-2 spike protein — the viral molecule responsible for recognizing and invading cells. The change, which is called P681R and transforms a proline residue into an arginine, falls within an intensely studied region of the spike protein called the furin cleavage site. The presence of this short string of amino acids set off alarm bells when SARS-CoV-2 was first identified in China, because it is associated with heightened infectivity in other viruses such as influenza, but had not previously been found in other sarbecoviruses, the family of coronaviruses to which SARS-CoV-2 belongs. “This little insert sticks out and hits you in the face,” says Gary Whittaker, a virologist at Cornell University in Ithaca, New York.
Here is what happens:
Now proline is a special case amino acid with no charge. Arginine is a positively charged molecule which adds to the binding potential. They continue
To penetrate cells, the SARS-CoV-2 spike protein must be cut twice by host proteins. In the SARS-CoV-1 virus that causes severe acute respiratory syndrome (SARS), both incisions occur after the virus has locked on to a cell. But with SARS-CoV-2, the presence of the furin cleavage site means that host enzymes (including one called furin) can make the first cut as newly formed viral particles emerge from an infected cell. These pre-activated viral particles can then go on to infect cells more efficiently than do particles requiring two cuts, says Whittaker.
The furin cut point has been the concern about a man made virus. Namely allowing this furin cut enables mutations that can become more aggressive rather than less.
It is for this reason that a vaccine including this spike variant is essential now. This demands Government leadership which unfortunately seems grossly lacking. Frankly it is a 20 min lab experiment, so why not do it! Before the next variant emerges. Or it may already be here and even worse.
It is a shame given what we know and what we can do.
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