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Probing the shape of a hydrophobic pocket in the active site of δ ‐opioid antagonists
Author(s) -
Santagada Vincenzo,
Caliendo Giuseppe,
Severino Beatrice,
Perissutti Elisa,
Ceccarelli Francesca,
Giusti Laura,
Mazzoni Maria Rosaria,
Salvadori Severo,
Temussi Piero Andrea
Publication year - 2001
Publication title -
journal of peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 66
eISSN - 1099-1387
pISSN - 1075-2617
DOI - 10.1002/psc.331
Subject(s) - chemistry , antagonism , selectivity , stereochemistry , side chain , peptide , opioid receptor , structure–activity relationship , biological activity , hydrophobic effect , opioid , receptor , combinatorial chemistry , biochemistry , in vitro , organic chemistry , catalysis , polymer
The change of selectivity and the induction of antagonism by the insertion of 1,2,3,4‐tetrahydroisoquinoline‐3‐carboxylic acid (Tic) in the second position of several opioid peptides have led to the interpretation of Tyr‐Tic as a specific message domain for δ ‐opioid antagonists and to the discovery of dipeptides with substantial opioid activity. Selectivity and activity increase enormously when Tyr is substituted by 2′,6′‐dimethyl tyrosine (Dmt), hinting that the side chain of Dmt fits a hydrophobic cavity of the receptor very tightly and precisely. We have investigated the specificity of this fit by systematic changes of the substituents on the aromatic ring of Tyr. Mono‐ and disubstitutions different from 2′,6′‐ invariably lead to catastrophic decreases of activity. The only substitution compatible with retention of substantial antagonism is 2′‐methyl. An analysis of the conformational properties of all analogues reveals that substitutions do not affect the global shape of the molecule significantly. Accordingly, it is possible to use the shape of the different side chains to map the hydrophobic cavity of the receptor. The resulting complementary image is funnel shaped. Copyright © 2001 European Peptide Society and John Wiley & Sons, Ltd.