Characterization of the bioactive conformation of the C-terminal tripeptide Gly-Leu-Met-NH2 of substance P using [3-prolinoleucine10]SP analogues.
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 chi1 angle and a trans conformation around the chi2 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.
Quancard
Jean
J
UMR 7613 Paris 6-CNRS, Université Pierre et Marie Curie, Paris, France.
Karoyan
Philippe
P
Sagan
Sandrine
S
Convert
Odile
O
Lavielle
Solange
S
Chassaing
Gérard
G
Lequin
Olivier
O
D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D006801:Humans; D007930:Leucine / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D018040:Receptors, Neurokinin-1 / Q000378:metabolism; D013373:Substance P / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D010446:Peptide Fragments; D018040:Receptors, Neurokinin-1; D013373:Substance P; D007930:Leucine