FIGURE 7.

Characterization of the binding pocket of PP docked in the hY₄R comparative model. A, side view of PP (purple) docked to hY₄R (cyan). Residues found to be important in the activation of hY₄R by hPP are labeled. Predicted interactions are indicated by dotted red lines (salt bridge between Asp^6.59 and Arg³⁵ and hydrogen bond between Arg³³ and Asn^7.32). B, top-down view of the same docked model. C, two docked models show the variability in ECL1. The model shown in gray has a significantly longer ECL1 than that shown in cyan. Trp^2.70, which was experimentally shown to be important in hY₄R activation by PP, is shown to be in different proximity to PP depending on the size of ECL1. D, side view of the same docked model shown in A and B. Residues experimentally shown to be inactive in the binding of hPP to hY₄R are indicated in black. The disulfide bond in ECL2 is also shown in yellow. a = His^7.39; b = Gln^3.32; c = Phe^6.54; d = His^6.62; e = Tyr^5.38; f = His^5.34; g = Trp^5.29; h = Phe^4.80; i = Glu^4.67; j = Glu^4.79; k = Lys^4.72; and l = Asp^4.83.