D614G Mutation Alters SARS-CoV-2 Spike Conformation and Enhances Protease Cleavage at the S1/S2 Junction
S. Gobeil, Katarzyna Janowska, Shana McDowell, Katayoun Mansouri, Robert Parks, Kartik Manne, Victoria Stalls, Megan Kopp, Rory Henderson, Robert J. Edwards, Barton F. Haynes, Priyamvada Acharya
Abstract
The severe acute respiratory coronavirus 2 (SARS-CoV-2) spike (S) protein is the target of vaccine design efforts to end the coronavirus disease 2019 (COVID-19) pandemic. Despite a low mutation rate, isolates with the D614G substitution in the S protein appeared early during the pandemic and are now the dominant form worldwide. Here, we explore S conformational changes and the effects of the D614G mutation on a soluble S ectodomain construct. Cryoelectron microscopy (cryo-EM) structures reveal altered receptor binding domain (RBD) disposition; antigenicity and proteolysis experiments reveal structural changes and enhanced furin cleavage efficiency of the G614 variant. Furthermore, furin cleavage alters the up/down ratio of the RBDs in the G614 S ectodomain, demonstrating an allosteric effect on RBD positioning triggered by changes in the SD2 region, which harbors residue 614 and the furin cleavage site. Our results elucidate SARS-CoV-2 S conformational landscape and allostery and have implications for vaccine design.