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. 2008 Dec 22;105(52):20711–20715. doi: 10.1073/pnas.0809086106

Fig. 2.

Fig. 2.

HIL-18–ectvIL-18BP interface. (A) Three binding pockets on hIL-18 surface. (Center) EctvIL-18BP and hIL-18 complex in a top-down view as seen in Fig. 1; hIL18 is shown as surface presentation and colored gray, and ectvIL-18BP is drawn as a ribbon diagram with β-sheets colored in yellow. Binding sites A–C on the hIL-18 surface are colored red, orange, and cyan, respectively. EctvIL-18BP residues involved in binding hIL-18 are shown as sticks. (Insets) Interactions involved in the respective binding site between ectvIL-18BP and hIL-18. (B) Remodeling of hIL-18 at site A. The coloring scheme is the same as in Fig. 1C. Tyr-1, Lys-53, Ser-66, and Pro-57 are shown as sticks. Notice the drastic repositioning of the side chains of Tyr-1 and Lys-53 at the carboxyl terminus of hIL-18 upon binding ectvIL-18BP. (C and D) Results of the conformational change upon ectvIL-18BP binding, yielding a new binding cavity/pocket for Tyr-53 and Phe-67 of ectvIL-18BP (shown as sticks). The ligand-free hIL-18 is shown as a surface presentation in blue in C. The complexed hIL-18 in the current crystal structure is shown as surface model in green. Notice that the absence of Phe-67 pocket and the steric clash on Tyr-53 would occur with the ligand-free state of hIL-18. The 2 key hIL-18 residues, Lys-53 and Tyr-1 are labeled as bold italic letters.