Pancreatic Polypeptide is Recognized by Two Hydrophobic Domains of the Human Y4 Receptor Binding Pocket [Computational Biology]

December 27th, 2013 by Pedragosa-Badia, X., Sliwoski, G. R., Dong Nguyen, E., Lindner, D., Stichel, J., Kaufmann, K. W., Meiler, J., Beck-Sickinger, A. G.

Structural characterization of the human Y4 receptor (hY4R) interaction with human pancreatic polypeptide (hPP) is crucial, not only for understanding its biological function but also for testing treatment strategies for obesity that target this interaction. Here, the interaction of receptor mutants with pancreatic polypeptide analogs was studied through double cycle mutagenesis. To guide mutagenesis and interpret results, a 3-dimensional comparative model of the hY4R-hPP complex was constructed based on all available class A G protein-coupled receptor (GPCR) crystal structures and refined using experimental data. Our study reveals that residues of the hPP and the hY4R form a complex network consisting of ionic interactions, hydrophobic interactions and hydrogen binding. Residues Tyr2.64, Asp2.68, Asn6.55, Asn7.32 and Phe7.35 of Y4R are found to be important in receptor activation by hPP. Specifically, Tyr2.64 interacts with Tyr27 of hPP through hydrophobic contacts. Asn7.32 is affected by modifications on position Arg33 of hPP, suggesting a hydrogen bond between these two residues. Likewise we find that Phe7.35 is affected by modifications of hPP in position 33 and 36, indicating hydrophobic interactions between these three amino acids. Taken together, we demonstrate that the top of transmembrane helix 2 (TM2) and the top of transmembrane helices 6 and 7 (TM6-TM7) form the core of the peptide binding pocket. These findings will contribute to the rational design of ligands that bind the receptor more effectively to produce an enhanced agonistic or antagonistic effect.