Figure 1
Hydrogen bonds (yellow dashes) in ABF between (a) iodide B71 and TrpH100 NE1 and (b) iodide B91 and the main-chain N atom of PheH105. (c) Triiodide B21–B23 (blue spheres) in a surface pocket of PPE. The triiodide make van der Waals contacts with backbone atoms of Asn115 and Ser116 on one side and the side chain of Gln119 on the other. The close proximity of Wat153 (red sphere), which is 3.06 Å from B21 and 3.34 Å from B22, suggests that it binds electrostatically to the triiodide. (d) Example of a pentaiodide molecule (sites B21–B25) binding in a partially solvent-exposed pocket formed between two symmetry-related molecules of XI. The pentaiodide is tethered at each end by hydrogen bonds (yellow dashes) formed with Gln234 NE2 and Lys240 NZ. The central three atoms contact through van der Waals interactions. The symmetry-related protein molecule is shown in green. The anomalous difference Fourier map contoured at 4σ is shown in red mesh. |