Figure 5.

RCC3 locks All RBDs into a singular orientation. Schematic representation of RCC3 disulfide mutation expected RBD behavior (modeled from PDB 6VXX), viewed from the “top” (left) and “side” (center) and zoomed in to show the engineered disulfide (right) (A). 2D class averages (top) and 3D reconstruction (bottom) of negative stain EM images of the RCC3_KV (B) and RCC3_PP (C) designs demonstrate all particles contained all three RBDs in the “closed” configuration without disrupting the S2 subunit. Spike particles were observed by negative stain EM images to be stable without significant degradation up to 27 days (D). Scale bars in (D) indicate 100nm and white circles highlight individual particles.