title: Hydrogen bonding interaction of thyrotropin-releasing hormone (TRH) with transmembrane tyrosine 106 of the TRH receptor.
abstract: Thyrotropin-releasing hormone (TRH, pyroglutamic acid-histidine-proline-amide) binds to a seven-transmembrane-spanning, G protein-coupled receptor. We tested the hypothesis that Tyr106 of the third transmembrane helix of the TRH receptor (TRH-R) binds pyroglutamyl of TRH by mutating Tyr106 to Phe and replacing the ring carbonyl of the TRH pyroglutamyl moiety with a methylene group ([Pro1]TRH). Compared to the affinity of wild-type TRH-R for TRH, the affinities of [Phe106]TRH-R for TRH and of wild-type TRH-R for [Pro1]TRH were 100,000- and 110,000-fold lower, respectively. The affinity of [Phe106]TRH-R for [Pro1]TRH was only 16-fold lower than that for TRH, demonstrating a lack of additivity of the effects of these changes in the receptor and ligand. These data provide compelling evidence that the hydroxyl group of Tyr106 of the TRH-R binds the TRH pyroglutamyl carbonyl group. To our knowledge, this represents the highest affinity, non-covalent bond yet observed between single functional groups of a GPCR and ligand and is the first delineation of a direct binding interaction between a residue in the transmembrane core of a GPCR and a specific moiety of a peptide agonist.
authors.affiliation: Department of Medicine, Cornell University Medical College, New York, New York 10021.
authors.forename: J H
authors.initials: JH
authors.lastname: Perlman
authors.forename: C N
authors.initials: CN
authors.lastname: Thaw
authors.forename: L
authors.initials: L
authors.lastname: Laakkonen
authors.forename: C Y
authors.initials: CY
authors.lastname: Bowers
authors.forename: R
authors.initials: R
authors.lastname: Osman
authors.forename: M C
authors.initials: MC
authors.lastname: Gershengorn
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006860:Hydrogen Bonding; D007295:Inositol Phosphates / Q000378:metabolism; D051379:Mice; D016297:Mutagenesis, Site-Directed; D018025:Receptors, Thyrotropin-Releasing Hormone / Q000737:chemistry* / Q000378:metabolism; D013329:Structure-Activity Relationship; D013973:Thyrotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D014162:Transfection; D014443:Tyrosine
chemical_list: D007295:Inositol Phosphates; D018025:Receptors, Thyrotropin-Releasing Hormone; D014443:Tyrosine; D013973:Thyrotropin-Releasing Hormone