Fig. 3.

Coaxial alignment of P3 and P4 in the absence of ligand. (A-C) Cartoon depicting the P3 and P4 helices as observed in (A) apo-6WJR (cyan), (B) holo-3F2Q (magenta), and (C) apo-2YIF (gray). Approximate helical axes (depicted as dotted lines) for P3 and P4 are aligned in apo-6WJR (A), and misaligned (kinked) in holo-3F2Q (B) and apo-2YIF (C), which is further illustrated in the reduction of the major groove (red arrows) formed between the two helices, taken as the distance between the phosphorus atoms of residues 46 and 58. (D-F) Expanded view of the P3/P4 helical junction in (A), (B), and (C), respectively, whose area is indicated by the black box in (A). The FMN ligand is shown as yellow ball-and-stick.