They were candid: the genome of SARS-CoV-2 as it had emerged in Wuhan carried coding for two notable features that required explaining. These two features were unexpected, insofar as they hadn’t been seen before in other known SARS-like coronaviruses (although they were not unique among coronaviruses generally, and they had parallels in other viruses too). Both features lay on the spike protein, the cell grabber. The first was the receptor-binding domain. The second was the furin cleavage site, which allowed the spike to cleave, and thereby fuse to the cell membrane, in response to a tickle
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