FIG 11.

Model for the effects of two evolutionary changes on SARS-CoV-2 S gp function. The conformational transitions of the SARS-CoV-2 S gp during functional activation by ACE2 binding and proteolytic cleavage are depicted. The proposed effects of changes in S gp reactivity/triggerability on viral phenotypes follow from studies of other class I viral envelope glycoproteins (33, 63, 67, 68). The wild-type, FurinMut, and D614G S glycoproteins are positioned along the pathway according to their phenotypes.