TY - JOUR
T1 - Key differences in molecular complexes of the cholecystokinin receptor with structurally related peptide agonist, partial agonist, and antagonist
AU - Arlander, Sonnet J.H.
AU - Dong, Maoqing
AU - Ding, Xi Qin
AU - Pinon, Delia I.
AU - Miller, Laurence J.
PY - 2004/9
Y1 - 2004/9
N2 - The molecular basis of docking of receptor ligands having differences in biological activity and their subsequent effects on receptor conformation represent areas of great interest. In this work, we focus on the sulfated tyrosyl residue in position 27 of cholecystokinin (CCK) and its spatial approximation with the type A CCK receptor residue Arg197 that has been predicted from mutagenesis experiments. We have examined the requirement for sulfation of this residue in a series of structurally related peptide agonists, partial agonists, and antagonists using assays of receptor binding and biological activity. Whereas sulfation of CCK position 27 was critical for affinity and potency of a full agonist, it had progressively less effect as the biological activity of the ligand was reduced. It had an intermediate effect on the partial agonist and no effect on the antagonist. In addition, photoaffinity labeling was used to determine the spatial approximations between the receptor and residue 27 of the agonist and antagonist in this series. Direct photoaffinity labeling with a full agonist probe confirmed the spatial approximation of ligand residue 27 and receptor residue Arg197 in the active complex. Of note, the analogous antagonist probe labeled a distinct region within the receptor amino terminus, confirming a key structural difference in active and inactive complexes.
AB - The molecular basis of docking of receptor ligands having differences in biological activity and their subsequent effects on receptor conformation represent areas of great interest. In this work, we focus on the sulfated tyrosyl residue in position 27 of cholecystokinin (CCK) and its spatial approximation with the type A CCK receptor residue Arg197 that has been predicted from mutagenesis experiments. We have examined the requirement for sulfation of this residue in a series of structurally related peptide agonists, partial agonists, and antagonists using assays of receptor binding and biological activity. Whereas sulfation of CCK position 27 was critical for affinity and potency of a full agonist, it had progressively less effect as the biological activity of the ligand was reduced. It had an intermediate effect on the partial agonist and no effect on the antagonist. In addition, photoaffinity labeling was used to determine the spatial approximations between the receptor and residue 27 of the agonist and antagonist in this series. Direct photoaffinity labeling with a full agonist probe confirmed the spatial approximation of ligand residue 27 and receptor residue Arg197 in the active complex. Of note, the analogous antagonist probe labeled a distinct region within the receptor amino terminus, confirming a key structural difference in active and inactive complexes.
UR - http://www.scopus.com/inward/record.url?scp=4944226721&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=4944226721&partnerID=8YFLogxK
U2 - 10.1124/mol.104.001396
DO - 10.1124/mol.104.001396
M3 - Article
C2 - 15322246
AN - SCOPUS:4944226721
SN - 0026-895X
VL - 66
SP - 545
EP - 552
JO - Molecular pharmacology
JF - Molecular pharmacology
IS - 3
ER -