Figure 6.

Unresolved questions regarding IL-18 subfamily signaling. A) IL-1R signaling ternary complex. IL-1β, IL-1RI and IL-1RAcP are colored in green, cyan and magenta (PDB ID 4DEP). Binding sites A and B are shown in red and orange spheres, respectively. B) A model of IL-18 (yellow):IL-18Rα (cyan):IL-18Rβ (magenta) based on the structure of IL-1β:IL-1RI:IL-1RAcP ternary complex. Putative receptor binding sites I (grey), II (grey) and III (blue) on IL-18 are shown as spheres. Notice site III is not involved in binding of either IL-18R in this model.