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Conformationally Constrained CCK8 Analogues Obtained from a Rationally Designed Peptide Library as Ligands for Cholecystokinin Type B Receptor
Author(s) -
De Luca Stefania,
Saviano Michele,
Della Moglie Raffaella,
Digilio Giuseppe,
Bracco Chiara,
Aloj Luigi,
Tarallo Laura,
Pedone Carlo,
Morelli Giancarlo
Publication year - 2006
Publication title -
chemmedchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.817
H-Index - 100
eISSN - 1860-7187
pISSN - 1860-7179
DOI - 10.1002/cmdc.200600054
Subject(s) - cholecystokinin , rational design , cholecystokinin receptor , chemistry , peptide , stereochemistry , receptor , ligand (biochemistry) , cyclic peptide , binding site , biochemistry , biology , genetics
A library of 14 cyclic peptide analogues derived from the octapeptide C‐terminal sequence of the human cholecystokinin hormone (CCK(26–33), or CCK8) was designed, synthesized, and characterized. The 14 peptide analogues were rationally designed to specifically interact with the CCK type B receptor (CCK B ‐R) on the basis of the structure of the bimolecular complex between CCK8 and the third extracellular loop of CCK B ‐R, namely CCK B ‐R(352–379). The rational design of new ligands for CCK B ‐R has relied on stabilization by cyclic constraints of the structural motifs that bring the key residues of the ligand (especially Trp 30, Met 31, and Phe 33) in the proper spatial orientation for optimal interaction with the receptor. The binding affinity of the new ligands for CCK B ‐R was assessed by displacement experiments of 111 In‐radiolabeled CCK8 in cells that overexpress the CCK B receptor. The new ligands generally showed binding affinities lower than that of parent CCK8, with the best compounds having IC 50 values around 10 μ M . Structure–activity relationship data show that preservation of the Trp 30–Met 31 motif is essential and that the Phe 33 side chain must be present. NMR conformational studies of the compound with maximal binding affinity ( cyclo ‐B11, IC 50 =11 μ M ) in DPC micelles shows that this compound presents a turn‐like conformation centered at the Trp 30–Met 31 segment, as planned by rational design. Such a conformation is stabilized by its interaction with the micelle rather than by the cyclic constraint.