Figure 4.

Aristolochene synthase–Mg²⁺₃-PP_i complex. (a) Simulated annealing omit maps of the PP_i anion (blue) and Mg²⁺ ions (red) contoured at 3σ. The Mg²⁺ ions are shown as grey spheres and water molecules appear as red spheres. (b) Same orientation as (a) showing selected metal coordination and hydrogen bond interactions. (c) Superposition of aristolochene synthase and trichodiene synthase (green) active sites in their Mg²⁺₃-PP_i complexes. (d) Least-square superposition of 300 Cα atoms between unliganded (blue) and Mg ²⁺₃-complexed (green) aristolochene synthase. Glycerol molecules are omitted from both structures for clarity. Significant conformational changes are triggered in the indicated helices and loops by Mg²⁺₃-PP_i binding.