Fig 1: SDS-PAGE analysis of purified plant-produced gRBD and dRBD proteins. RBD protein variants were purified from N. benthamiana using anti-FLAG antibody resin. (A) gRBD—3 or 6 µg plant-produced glycosylated RBD; dRBD—3 or 6 µg plant-produced deglycosylated RBD; BSA standards—1.0, 2.5 and 5.0 µg; M—color prestained protein standard (NEB). (B) Western blot analysis of gRBD and dRBD using anti-Flag antibody: pp Endo H—plant-produced and purified Endo H protein with molecular mass of ~30 kDa [37]. pp PNGase F—plant-produced and purified PNGase F protein with a molecular mass of ~35 kDa [36]. (C) Western blot analysis of gRBD and dRBD using commercially available, purified anti-SARS-CoV-2 S protein S1 mAb (cat. no. 945102, BioLegend). (D) Western blot analysis of gRBD and dRBD using commercially available anti-RBD antibody (cat. no. MBS2563840, MyBiosource, San Diego, CA, USA); commercial spike protein—COVID 19 spike protein (RBD) active protein, sequence positions Arg319–Phe541 (MBS2563882, MyBiosource); pp—plant-produced; R—reducing; NR—non-reducing condition.