The furin cleavage site in SARS-CoV-2 uses an arginine codon (CGG) uncommon in sarbecoviruses
3 events · 2 assessments
Reassessed: still Verified
verdict confidence 0.90 → 0.92
Assessed Verified
verdict confidence 0.90
The molecular facts behind this claim are well established. The furin cleavage site inserted at the S1/S2 junction of the SARS-CoV-2 spike protein (the PRRA motif) contains two consecutive arginine residues encoded by CGG codons, and CGG is indeed an uncommon way to encode arginine in sarbecoviruses and coronaviruses more broadly. Codon-usage data bear this out: the relative synonymous codon usage of CGG is very low in related bat and pangolin coronaviruses, and CGG accounts for only roughly 3–5% of arginine codons even within the SARS-CoV-2 genome itself. This narrow factual statement is not in dispute. What *is* vigorously contested — and is a separate question — is what the codon choice implies about the virus's origin: some researchers have highlighted the rare CGG-CGG doublet as suggestive of laboratory manipulation, while others note that rare codons occur naturally, that CGG appears elsewhere in the genome, and that codon rarity alone cannot establish provenance. That interpretive debate does not bear on the truth of the codon-usage fact stated here.
Claim entered the graph