Fig. 4: The effect of mutations in the membrane-interacting segments on membrane fusion.
From: Cryo-EM structure of SARS-CoV-2 postfusion spike in membrane
a, Structure-guided design of mutations in the s816–834, FPPR, FP and CT regions. The wild-type sequences are shown in black and the mutated residues in red. aa, amino acids. b,c, Cell–cell fusion mediated by the G614 S and the designed mutants. HEK293T cells transfected with the full-length S protein expression plasmids were fused with ACE2-expressing cells. Cell–cell fusion led to reconstitution of the α and ω fragments of β-galactosidase to form an active enzyme, and the fusion activity was then quantified using a chemiluminescent assay. Cells not transfected with ACE2 were used as negative (neg.) controls. The experiment was repeated four times with similar results. Data are mean ± s.d. d, Cell–cell fusion mediated by the Delta-variant S and its mutants. The negative control conditions included no spike and no ACE2, no spike, no ω fragment of β-galactosidase and no α fragment of β-galactosidase. The experiment was repeated three times with similar results. Data are mean ± s.d.
