Space-filling models of A) AIP-III and B) agonist AIP-III d-L7 displaying hydrophobic (yellow) and hydrophilic (green) surfaces. Ile1 is proposed to act as the activation anchor, and Phe5, Leu6, and Leu7 as the hydrophobic knob, in the native AIP-III. In turn, Phe5 may serve as an alternate activation anchor, and Ile1, d-Leu7, and Leu6 as an alternate hydrophobic knob, in AIP-III d-L7.