Figure 6.

Transition-state model for the PaHisG_S-catalyzed reaction. (A) Transition structure with magnesium, (B) transition structure with manganese, and (C) overlay of the transition structures with magnesium and manganese. Substrates are represented as stick models, side-chain mimics as wireframe, and metal ions and water oxygens as spheres. Carbon is in either cyan or yellow for substrates and in gray for side-chain mimics, with oxygen in red, nitrogen in blue, phosphorus in orange, magnesium in green, and manganese in purple. Hydrogens are omitted for simplicity. Partial bonds and metal ion coordination bonds are represented by dashed lines. Distances are shown for the N1–C1 and the C1–O1 bonds. Key residue side-chain mimics are labeled, and the prime denotes a residue of the adjacent subunit in the PaHisG_S dimer.²⁹