Molecular complex of cholecystokinin-8 and N-terminus of the cholecystokinin A receptor by NMR spectroscopy.
The bimolecular complex of the C-terminal octapeptide of cholecystokinin, CCK-8, with the N-terminus of the CCK(A)-receptor, CCK(A)-R(1-47), has been structurally characterized by high-resolution NMR and computational refinement. The conformation of CCK(A)-R(1-47), within the lipid environment used for the spectroscopic studies, consists of a well-defined alpha-helix (residues 3-9) followed by a beta-sheet stabilized by a disulfide linkage between C18 and C29, leading to the first transmembrane alpha-helix (TM1). Titration of CCK(A)-R(1-47) with CCK-8 specifically affects the NMR signals of W39 of the receptor, in a saturable fashion. This association is specific for CCK-8; no association was observed upon titration of CCK(A)-R(1-47) with other peptide hormones. The ligand/receptor complex was characterized by intermolecular NOEs between Tyr(27) and Met(28) of CCK-8 and W39 of CCK(A)-R(1-47). These findings suggest that CCK-8 binds to CCK(A) with the C-terminus within the seven-helical bundle and the N-terminus of the ligand, projecting out between TM1 and TM7, forming specific interactions with the N-terminus of the CCK(A) receptor. This mode of ligand binding, consistent with published mutagenesis studies, requires variation of the interpretation of recent findings from photoaffinity cross-linking studies.
Pellegrini
M
M
Department of Molecular Pharmacology, Division of Biology & Medicine, Brown University, Providence, Rhode Island 02912, USA.
Mierke
D F
DF
D000595:Amino Acid Sequence; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019920:Photoaffinity Labels; D017433:Protein Structure, Secondary; D043886:Receptor, Cholecystokinin A; D011949:Receptors, Cholecystokinin / Q000378:metabolism*; D012844:Sincalide / Q000378:metabolism*
D046911:Macromolecular Substances; D019920:Photoaffinity Labels; D043886:Receptor, Cholecystokinin A; D011949:Receptors, Cholecystokinin; D012844:Sincalide