Figure 7

Sodium ion binding site in Pil _Bac1 ΔN. A: Sodium ion binding site in chain B. The Na⁺ ion is coordinated by the backbone oxygens of Leu36 and Phe44, as well as the side chain oxygen of Asn38 and three water molecules. B: Homologous ion binding site in chain A with a superposed sodium ion from chain B. C: Superposition of the ion binding site in chain B, with the homologous residues in chain A. The carbonyl oxygen of Leu36 is moved further away from the sodium in chain A with respect to chain B increasing the distance to the Na⁺ ion to 3.7 Å. Molecules from chain A are shown in grey, molecules from chain B in purple. Distances in Å to the position of the sodium ion in chain B are shown in black.