Identification of Receptor-Binding Pharmacophores of Growth-Hormone-Releasing Factor in Rat Adenopituitary
Notice bibliographique
Résumé
Previous structure-activity studies on growth-hormone-releasing factor (GRF) have mainly been carried out in pituitary cell culture assays. In such systems, the molecular features necessary to increase GRF receptor affinity cannot be fully distinguished from those that improve proteolytic resistance. To assess the affinity of GRF analogues, we have recently characterized [125I-Tyr10]hGRF(l-44)NH<sub>2</sub> binding to rat adenopituitary, developing a reliable binding assay in which GRF-carboxamide-related peptides are stable. In the present study, we have determined the binding affinity of two series of analogues in which the entire sequence of hGRF(1-29)NH2 was scanned with D-amino acid and alanine substitutions. To further document their potency, we have evaluated the ability of representative candidates of each series to stimulate cAMP production. In the first series, a D-amino acid substitution at Ala4, He5, Phe6, Thr7, Val13, Gin16, Leu17, Ala19, Arg20 and He26 decreased drastically the binding affinity of hGRF(1-29)NH<sub>2</sub> while it induced a smaller decrease at Tyr1, Asp3, Ser9, Tyr10, Arg11, Lys12, Leu14, Ala15, Ser18, Lys21, Leu22, Leu23, Gin24, Met27 and Ser28. Interestingly, a D-substitution in position 8 generated an analogue exhibiting a significantly greater binding affinity than hGRF(1-29)NH<sub>2</sub>, while it had no influence on hGRF(1-29)NH<sub>2</sub> affinity at Ala2, Asp25 and Arg29. Adenylate cyclase activities of [D-Tyr1], [D-Tyr10] and [D-Arg20]hGRF(1-29)NH<sub>2</sub> correlate with their binding affinity. In the second series, the largest decrease of binding affinity was observed with an alanine substitution at Tyr1, Asp3, He5, Phe6, Tyr10, Arg11, Lys12, Leu14, Leu17, Arg20 and Lys21. Replacement of Thr7, Ser9, Val13, Gin16, Ser18, Leu23, Gin24, Asp25, He26, Met27 or Arg29 by an Ala residue induced a smaller decrease of binding affinity, while it generated analogues showing a comparable affinity to hGRF(1-29)NH<sub>2</sub> at Leu22 or Ser28. An Ala-substitution significantly increased the binding affinity of hGRF(1-29)NH<sub>2</sub> at Ala8 and Ala15. Adenylate cyclase activities of [Ala9], [Ala16], [Ala17], [Ala18], [Ala20], [Ala22], [Ala26] and [Ala28]hGRF(1-29)NH<sub>2</sub> were also in agreement with their binding affinities. Altogether these results demonstrate that residues Ala4, Val13, Ala19 and He26 are involved in the maintenance of a hGRF(1-29)NH<sub>2</sub> structure for optimal receptor binding while residues Tyr1, Asp3, Tyr10, Arg11, Lys12, Leu14, Leu17, Arg20 and Lys21 are responsible for receptor contacts. Since the binding affinities are low for both a D- and Ala-substitution at He5 and Phe6, these two amino acids are probably important for structural and receptor contact roles. In addition, it suggests that residues involved in receptor binding are also required for receptor activation.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».