Figure 3.

Comparison of TPP riboswitch structures, bound by thiamine, TPP and TPPc. (A) Comparison of thiamine- (colored) and TPPc-bound (light gray) riboswitch structures. Metal ions and water molecules were omitted from the TPPc structure for clarity. Arrows indicate shifts in positions of nucleotides near thiamine. THG, thiamine head group; Tz, thiazole. (B) Comparison of TPPc- (colored) and TPP-bound (light gray) structures. Ligand-bound Mn²⁺ ions and coordinated waters in the TPPc structure are depicted in violet and red spheres, respectively; ions and coordinated water molecules for the TPP-bound structure are shown with small spheres (in light gray). Hydrogen bonds and metal-ligand coordination are shown with dashed lines.