Figure 2.

Kinetic substrate trapping using either reduced or oxidized PDI variants. Shown are reaction schemes diagramming the kinetic trapping of either the wild-type enzyme, the CXXA variant, or the intervening sequence variants with substrate protein, starting from either the reduced (A) or oxidized (B) state. Bonds that are made or broken during catalysis are shown in red. t₀, the initial state; t₁ and t₂, intermediate states; t_trap, reaction state when stopped with NEM; t_final, protein-substrate complex, or lack thereof, isolated after IP.