Fig. 3.

GcoA-F169 in WT GcoA and the substrate access loop are significantly displaced with bound syringol. MD simulations with bound guaiacol indicate that GcoA-F169 (A) and the substrate access lid (B) are relatively stable (Movies S1 and S3). Introducing syringol results in increased flexibility of GcoA-F169 (C) and the substrate access loop (D) (Movies S2 and S4). In A–D, the position of each of the labeled Phe side chains (or, alternatively, the substrate access loop) is shown every 4 ns over the course of the 80-ns MD simulation. Substrate, the Phe side chains, and heme are shown in sticks, and the Fe atom and the O atom of a reactive heme-oxo intermediate are shown as spheres. Probability distributions are shown for the rmsd of the six ring carbons of GcoA-F169 from their crystal structure positions (E) and the reaction coordinates for opening/closing of the substrate access loop (as defined in SI Appendix; lower values indicate more open configurations) (F).