Fig 1: FXa suppresses viral entry by binding to and cleaving the SARS-CoV-2 S protein.a The binding affinity of FXa with full-length wild-type S protein, subunit S1, subunit S2, or RBD was quantified by ELISA (n = 9 biologically independent samples). Bounds of box is from 25% percentile to 75% percentile, horizontal bar indicates median, and whiskers indicate data ranges. b The binding affinity of FXa to VSV-SARS-CoV-2 viral particles was quantified by ELISA (n = 3 biologically independent samples). c The interaction between FXa protein and full-length S protein was examined with a pull-down assay. d The binding affinity at indicated concentrations of FXa was measured by ELISA (n = 3 biologically independent samples). e The cleavage of S protein by furin, TMPRSS2, and FXa after 3-hour incubation was analyzed by immunoblotting using an anti-S protein antibody (40591-T62, Sino Biological). f S protein was cleaved by FXa, followed by immunoblotting with an anti-RBD antibody (MAB10540-100, R&D) (left) and an anti-S2 antibody (MA5-35946, Invitrogen) (right). g The cleavage of VSV-SARS-CoV-2 by FXa or furin was analyzed by immunoblotting using an anti-S protein antibody (40591-T62, Sino Biological). The larger size of S protein from VSV-SARS-CoV-2 (~200 kD) compared to recombinant S protein (~150 kD) may be due to the glycosylation of the former. All data are representative of at least three independent experiments. a, b, d, data are presented as mean values ± SD. Statistical analyses were performed by two-sided Student’s t test (b) or one-way ANOVA models (a). Source data are provided as a Source Data file.