FIG. 3.

Coordination of Mg²⁺ in the Mg²⁺-AMPCPR complex. (A) Stereo diagram of the Mg²⁺-binding site. Mg²⁺ ions and a nucleophilic water molecule are represented as magenta spheres and a red sphere, respectively. AMPCPR is represented in stick formation and Corey-Pauling-Kultun color coding. The Fo-Fc electron density map for the Mg²⁺ ions and AMPCPR is contoured at the 3.0-σ level. (B) Schematic representation of the Mg²⁺-binding site. W, water; W4 is assumed to be the nucleophilic water.