Structural and conformational analogy between cholecystokinin and ergopeptines

The central nervous system (CNS) peptide cholecystokinin (CCK) and the ergopeptine alkaloids exhibit common pharmacology in the brain, particularly via catecholaminergic systems. We report here structural similarities between CCK and the ergot alkaloids, and the subsequent conformational analysis of the peptide undertaken to establish whether or not a three-dimensional relationship exists between the compounds. Two low-energy conformations of CCK that mimic the ergopeptine ergotamine are identified, one arising from an X-ray crystal structure and the other from a Dreiding model-based, computer-assisted search. The pharmacological, structural and conformational observations strongly support the hypothesis that CCK and the ergopeptines share common sites of action in the CNS.