Environmental mimic of receptor interaction: conformational analysis of CCK-15 in solution.

CCK-15, a peptide derived from the 115-membered CCK preprohormone, was the object of a comparative conformational analysis by NMR spectroscopy and molecular modeling methods. NMR data in several solvents demonstrate that the propensity of the peptide to fold into a helical conformation is intrinsic, not merely a consequence of the interaction with phosphatidylcholine micelles or with a putative receptor, as suggested by a previous study on CCK-8 (Pellegrini, M.; Mierke, D. Biochemistry 1999, 38, 14775-14783.). The prevailing CCK-15 conformer in a mixture 1,1,1,3,3,3-hexafluoroacetone/water reveals that the residues common to CCK-15 and CCK-8 assume very similar conformations. Our CCK-15 structure is consistent with the model of receptor interaction proposed by Pellegrini and Mierke and discloses possible novel interactions that involve a larger area of the putative receptor. The consensus structure between CCK-15 and CCK-8 shows a good superposition of the side chains of residues 12-14 with crucial moieties of two non-peptidic CCK-A antagonists.