Figure 3.

(A) N-Terminal active site in the X-ray crystal structure of the ΔE162 OxDC/oxalate complex. Carbon atoms in the protein and bound oxalate are colored green and cyan, respectively. The Co(II) ion is rendered as a pink sphere. (B) Overlay of the active sites of the Co(II)-substituted ΔE162 OxDC variant (C, green), WT OxDC (C, purple) with the Glu¹⁶² side chain in the “closed” orientation (PDB entry 1UW8), and WT OxDC (C, magenta) with the Glu¹⁶² side chain in the “open” orientation (PDB entry 1J58). Only the metal from the Co(II)-substituted ΔE162 OxDC variant is shown for the sake of clarity. (C) N-Terminal active site of WT OxDC (C and Mn, purple) with oxalate (C, orange) modeled in a “side on” conformation by placing the carboxylate oxygens in the two positions occupied by waters (blue spheres) in the wild-type structure (PDB entry 1UW8). The steric clash with Glu¹⁶² is denoted by an orange line. The oxygen atoms of metal-bound water molecules are rendered as red spheres, and metal–ligand coordinate bonds are shown as black dashed lines in all three images.