Figure 3.

RBD nonnative state shows incomplete disulfide formation and is prone to forming cross-linked aggregates. (a) Schematic of cysteines and disulfides (blue curves) in the RBD construct used in our experiments, derived from the crystal structure with PDB: 6YOR. In the full spike protein, C205 is bonded with an additional cysteine (C590 in full spike numbering) not included in our construct. In our numbering scheme, residue 1 of the RBD corresponds to residue 333 of the full spike protein. (b) SDS-PAGE gel, stained with Coomassie G-250 dye, loaded with Ox $\to$ Ox and Red $\to$ Ox refolded samples with or without 10 mM TCEP added before loading, as indicated above respective lanes. The inset on the left shows labeled molecular weight standards.