Hydrogen bonding interaction of thyrotropin-releasing hormone (TRH) with transmembrane tyrosine 106 of the TRH receptor.
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.
Perlman
J H
JH
Department of Medicine, Cornell University Medical College, New York, New York 10021.
Thaw
C N
CN
Laakkonen
L
L
Bowers
C Y
CY
Osman
R
R
Gershengorn
M C
MC
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
D007295:Inositol Phosphates; D018025:Receptors, Thyrotropin-Releasing Hormone; D014443:Tyrosine; D013973:Thyrotropin-Releasing Hormone