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. 2006 Oct 10;103(42):15422–15427. doi: 10.1073/pnas.0607058103

Fig. 5.

Fig. 5.

Details of contacts between IL-2 (shown in gray) and either IL-2Rα (Upper, shown in blue) or SP4206 (Lower, shown in yellow) at the three hot-spot residues found to be critical for binding: F42 (A), E62 (B), or Y45 (C). In A, note the fully buried nature of F42 in both complexes despite the difference in conformation of this residue between the two complexes. In B, IL-2Rα R36 forms a buried salt bridge with IL-2 E62. This interaction is structurally mimicked by the guanido group on SP4206. In C, Y45 is fully buried upon binding to IL-2Rα and forms a binding pocket for both the guanido group and the isobutyl moiety in SP4206.