Figure 2.

Optimized structures of HPPD complexed with different metal ions and isomers of HPPA: (a) Co²⁺ and enol; (b) Co²⁺ and ketone; (c) Fe²⁺ and enol; (d) Fe²⁺ and ketone. The geometries were optimized at the QM/MM (B3LYP/6-31+G∗: AMBER) level. The key distances in the figure are in angstroms. Cobalt, iron, carbon, oxygen, nitrogen, and hydrogen atoms are colored in pink, light green, cyan, red, blue, and white, respectively. The backbone of the protein is rendered in light blue. All QM atoms are represented as balls and sticks, and part of surrounding residues are rendered as sticks.