Fig. 4

Coordination sphere of the magnesium ion. The residues of the loop carrying the Mg²⁺ binding site are represented as sticks. The Mg²⁺ ion is coordinated by the main chain carboxyl groups of V189 and E192, and the side chain carboxyl group of D195. The octahedral coordination sphere is completed by three water molecules. The right panel shows a close-up view of the binding site, indicating the distances to the coordinating atoms in Å