Figure 6: Potential electron and proton movements during halide ion release.
From: Cobamide-mediated enzymatic reductive dehalogenation via long-range electron transfer
(a) Position of proximal iron–sulfur cluster, cobalt and 2,4,6-TBP substrate constrained by protein side chains. Within the constraints of the binding pocket, a leaving C2 substituent is not free to diffuse away from the substrate, a C4 halide may move to the upper cavity and a C6 halide may move to the substrate channel. It is not clear if the Co-water/hydroxyl ligand can be exchanged for a C2 or C6 halide with the substrate bound after reduction of PceA. (b) Exchangeable protons near C4 are present in the upper pocket in a network of ionizable side chains and water molecules. (c) Tyr246 may act as proton donor for C2 or C6. The view shows residues in front of panel a.
