“The spike (S) glycoprotein of the SARS-CoV-2 virus that emerged in 2019 contained a suboptimal furin cleavage site at the S1/S2 junction with the sequence 681 PRRAR/S 686. This cleavage site is required for efficient airway replication, transmission, and pathogenicity of the virus. …P681R significantly enhanced the ability of furin to cleave the peptide confirming that the arginine substitution is responsible for the enhanced cleavage of the B.1.617 S protein.
We speculate that enhanced S1/S2 cleavage seen in B.1.617 and B.1.1.7 [Alpha variant] (which contains P681H) may be contributing to the enhanced transmissibility of these SARS-CoV-2 variants.”
