title: The motilin pharmacophore in CHO cells expressing the human motilin receptor.
abstract: We performed a structure-activity study with the human motilin receptor, which was recently cloned from thyroid tissue. N-terminal fragments, Ala-analogs of motilin, and motilides were tested in a cell line that expresses the cloned human motilin receptor and apoaequorin. Full potency to induce calcium fluxes was obtained with N-terminal fragments of 14 amino acids. Motilin fragments 1-14 in which residues 1 (Phe), 4 (Ile), and 7 (Tyr) were replaced by Ala showed the largest reduction in potency. Only motilides with an enol configuration had markedly higher potencies compared to erythromycin A. The potencies to induce Ca(2+) fluxes correlated strongly with rabbit binding and contractility data, suggesting that the cloned receptor is indeed the motilin receptor, responsible for contractile effects. Conservation of the motilin pharmacophore in evolution indicates an important physiological role of motilin.
authors.affiliation: Department of Pathophysiology, Gut Hormone Lab, Center for Gastroenterological Research, Katholieke Universiteit Leuven, Leuven B-3000, Belgium.
authors.forename: Leen
authors.initials: L
authors.lastname: Thielemans
authors.forename: Inge
authors.initials: I
authors.lastname: Depoortere
authors.forename: Jozef
authors.initials: J
authors.lastname: Vanden Broeck
authors.forename: Theo L
authors.initials: TL
authors.lastname: Peeters
mesh_terms: D000331:Aequorin / Q000737:chemistry; D000409:Alanine / Q000737:chemistry; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D006224:Cricetinae; D004064:Digestive System / Q000737:chemistry; D004386:Duodenum / Q000378:metabolism; D004917:Erythromycin / Q000494:pharmacology; D005765:Gastrointestinal Agents / Q000494:pharmacology; D006801:Humans; D009037:Motilin / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011817:Rabbits; D011964:Receptors, Gastrointestinal Hormone / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D018013:Receptors, Neuropeptide / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D013329:Structure-Activity Relationship; D013552:Swine; D013961:Thyroid Gland / Q000378:metabolism
chemical_list: D005765:Gastrointestinal Agents; D011964:Receptors, Gastrointestinal Hormone; D018013:Receptors, Neuropeptide; C050802:motilin receptor; D000331:Aequorin; D009037:Motilin; D004917:Erythromycin; D000409:Alanine; D002118:Calcium