Open AccessCharacterization of the bioactive conformation of the C‐terminal tripeptide Gly‐Leu‐Met‐NH 2 of substance P using [3‐prolinoleucine10]SP analogues
Author(s) -
Quancard Jean,
Karoyan Philippe,
Sagan Sandrine,
Convert Odile,
Lavielle Solange,
Chassaing Gérard,
Lequin Olivier
Publication year - 2003
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1033.2003.03665.x
Subject(s) - tripeptide , conformational isomerism , stereochemistry , chemistry , residue (chemistry) , agonist , nuclear magnetic resonance spectroscopy , receptor , peptide , biochemistry , molecule , organic chemistry
Residue Leu10 of substance P (SP) is critical for NK‐1 receptor recognition and agonist activity. In order to probe the bioactive conformation of this residue, cis ‐ and trans ‐3‐substituted prolinoleucines were introduced in position 10 of SP. The substituted SP analogues were tested for their affinity to human NK‐1 receptor specific binding sites (NK‐1M and NK‐1m) and their potency to stimulate adenylate cyclase and phospholipase C in CHO cells transfected with the human NK‐1 receptor. [ trans ‐3‐prolinoleucine10]SP retained affinity and potency similar to SP whereas [ cis ‐3‐prolinoleucine10]SP shows dramatic loss of affinity and potency. To analyze the structural implications of these biological results, the conformational preferences of the SP analogues were analyzed by NMR spectroscopy and minimum‐energy conformers of Ac‐ cis ‐3‐prolinoleucine‐NHMe, Ac‐ trans ‐3‐prolinoleucine‐NHMe and model dipeptides were generated by molecular mechanics calculations. From NMR and modeling studies it can be proposed that residue Leu10 of SP adopts a gauche(+) conformation around the χ 1 angle and a trans conformation around the χ 2 angle in the bioactive conformation. Together with previously published results, our data indicate that the C‐terminal SP tripeptide should preferentially adopt an extended conformation or a PPII helical structure when bound to the receptor.