title: Analysis of structural requirements for TRH-potentiating peptide receptor binding by analogue design.
abstract: Previous studies established that the [125I-Tyr0]Ps4 derivative of TRH-potentiating peptide (Ps4), Ser-Phe-Pro-Trp-Met-Glu-Ser-Asp-Val-Thr, displays high affinity and selectivity for an orphan membrane receptor in rat anterior pituitary. To identify the sites in Ps4 that determine receptor binding affinity, we have synthesized and screened a panel of 15 single-point substituted analogues for their ability to displace bound [125I-Tyr0]Ps4. The affinity of [Tyr0]Ps4 for rat anterior pituitary membranes [inhibitory constant (Ki), approximately 5 nM] was drastically reduced by the substitution of either Tyr0 with Gly or Asp8 with Asn (Ki approximately 95 and approximately 51 nM, respectively). Deamination of [Tyr0]Ps4 also sharply reduced affinity (Ki approximately 1100 nM). In contrast, Ser1-->Ala, Pro3-->Ala and Thr10-->Val substitutions led to analogues showing a tenfold increase in binding affinity relative to the parent peptide. The change of Phe2-->Leu, Trp4-->Ala, Glu6-->Gln, Val9-->Thr and carboxamidation of Thr10 had no effect on binding affinity. The data suggest that substitutions of the amino-terminal group, Asp8 and Tyr0, have a marked effect on the ability of [Tyr0]Ps4 to compete with [125I-Tyr0]Ps4 for binding to TRH-potentiating peptide pituitary receptor.
authors.affiliation: Laboratoire de Bioactivation des Peptides, Institut Jacques Monod, Université Paris 7, France.
authors.forename: A
authors.initials: A
authors.lastname: Ladram
authors.forename: J J
authors.initials: JJ
authors.lastname: Montagne
authors.forename: M
authors.initials: M
authors.lastname: Bulant
authors.forename: P
authors.initials: P
authors.lastname: Nicolas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015195:Drug Design; D005069:Evaluation Studies as Topic; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*
chemical_list: D010446:Peptide Fragments; D011498:Protein Precursors; D011956:Receptors, Cell Surface; C089535:TRH-potentiating peptide receptor, rat; C057639:prepro-thyrotropin releasing hormone (160-169); D013973:Thyrotropin-Releasing Hormone