(A) Stereo view of the enlarged NPY binding sites of the two superimposed structures. Sec3 and the NPY motifs of Sso2 are shown as ribbons and sticks, respectively. Water molecules bound to the NPY motifs (directly or indirectly) are depicted as spheres with the same colors as the corresponding NPY motifs. (B, C) Separate stereo views of the two NPY binding sites. Sec3 molecules are shown as ribbons, with those residues hydrogen bonded to Sso2 or Sso2-bound water molecules additionally shown as sticks. The NPY motifs and waters are shown as sticks and spheres, respectively. All hydrogen bonds are depicted as dash lines. (D, E) Details of interactions between the NPY motifs of Sso2 (purple) and Sec3 (gray). The plots were generated using DIMPLOT in the LigPlot plus suite. Residues involved in hydrogen bond formation are shown as ball-and-stick, with oxygen, nitrogen, and carbon atoms colored in red, blue, and gray, respectively. Water molecules mediating intermolecular hydrogen bond formation are shown as cyan-colored spheres. Green dash lines indicate hydrogen bonds. Non-bonded residues involved in hydrophobic interactions are shown as spoked arcs. For clarity, only three of the seven bound water molecules are shown.