Figure 9.

Structure of SLO depicting the peptides affected by interactions with allosteric effector, OS. The SLO model (Protein Data Bank code 3PZW) is colored pale blue. Peptides, whose backbone HDX properties are impacted by interactions with OS, are colored as follows. Yellow, increased extent of exchange (not rate); salmon, increased rate of exchange. A, proposed communication network for OS-mediated allostery includes the conserved cation-π interaction (green sticks). The iron cofactor is represented as a dark gray sphere. The modeled substrate is depicted in spheres (orange, carbon; white, hydrogen). Side chains Thr-259 and Leu-541 at the substrate entrance are displayed in spheres for reference. The green highlighted area suggests the binding site for OS. B, a focused view of the cation-π interaction between Trp-130 and Arg-242. The conserved carboxylate, Asp-243, also forms hydrogen bonds to Trp-130 backbone.