Fig. 3: Signal peptide analysis of membrane-bound S proteins.

LC-MS/MS analysis of the N-terminus of S.PP, tPA.S.PP, and tPA.WT.S after either ACE2-Fc or CR3022 pull-down from cell membranes. Sequences are shown of the wt SP, tPA SP and the tPA SP linked to the wt SP (in red letters) upstream of the mature S protein sequence (in black letters). Cleavage events as predicted by SignalP-5.0 are indicated with scissors. The recovery rates of the different expected peptides are color-coded. LOD lower limit of detection.