Fig. 4.

Peptide agonists binding to GRPR. (A) Cross-section of the peptide-binding pocket of GRPR was shown as forest green surface, with GRP as pink ribbons and side chains of W21^G, V23^G, and M27^G displayed as pink sticks. (B and C) Structural alignment of GRP (green) and [D-Phe⁶, β-Ala¹¹, Phe¹³, Nle¹⁴] Bn (6–14) (gray), with enlarged views of detailed interactions at N19^G and F1^B.(D) The TM bottom pocket. (E) The hydrophobic cavities around the helical fragment of GRP. (F) The extracellular loops.