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Title Guanine nucleotide-binding protein regulation of melatonin receptors in lizard brain
Creator/Author Rivkees, S.A. ; Carlson, L.L. ; Reppert, S.M. (Harvard Medical School, Boston, MA (USA))
Publication Date1989 May 01
OSTI IdentifierOSTI ID: 5185879
Other Number(s)ISSN0027-8424; CODEN: PNASA
Resource TypeJournal Article
Resource RelationProceedings of the National Academy of Sciences of the United States of America ; Vol/Issue: 86:10
Subject550601 -- Medicine-- Unsealed Radionuclides in Diagnostics; MELATONIN-- RADIORECEPTOR ASSAY;RECEPTORS-- MOLECULAR STRUCTURE; BIOCHEMICAL REACTION KINETICS;BRAIN;CELL MEMBRANES;GUANINE;IODINE 125;LIGANDS;LIZARDS;MEMBRANE PROTEINS;MEMBRANES;PROTEINS
Related SubjectAMINES;ANIMALS;AROMATICS;AZAARENES;AZOLES;BETA DECAY RADIOISOTOPES;BODY;CELL CONSTITUENTS;CENTRAL NERVOUS SYSTEM;DAYS LIVING RADIOISOTOPES;ELECTRON CAPTURE RADIOISOTOPES;HETEROCYCLIC COMPOUNDS;HYDROXY COMPOUNDS;INDOLES;INTERMEDIATE MASS NUCLEI;IODINE ISOTOPES;ISOTOPE APPLICATIONS;ISOTOPES;KINETICS;MEMBRANE PROTEINS;MEMBRANES;NERVOUS SYSTEM;NUCLEI;ODD-EVEN NUCLEI;ORGANIC COMPOUNDS;ORGANIC NITROGEN COMPOUNDS;ORGANS;PROTEINS;PURINES;PYRROLES;RADIOISOTOPES;REACTION KINETICS;REPTILES;TRACER TECHNIQUES;TRYPTAMINES;VERTEBRATES
Description/Abstract Melatonin receptors were identified and characterized in crude membrane preparations from lizard brain by using {sup 125}I-labeled melatonin ({sup 125}I-Mel), a potent melatonin agonist. {sup 125}I-Mel binding sites were saturable; Scatchard analysis revealed high-affinity and lower affinity binding sites, with apparent K{sub d} of 2.3 {plus minus} 1.0 {times} 10{sup {minus}11} M and 2.06 {plus minus} 0.43 {times} 10{sup {minus}10} M, respectively.^Binding was reversible and inhibited by melatonin and closely related analogs but not by serotonin or norepinephrine.^Treatment of crude membranes with the nonhydrolyzable GTP analog guanosine 5{prime}-({gamma}-thio)triphosphate (GTP({gamma}S)), significantly reduced the number of high-affinity receptors and increased the dissociation rate of {sup 125}I-Mel from its receptor.^Furthermore, GTP({gamma}S) treatment of ligand-receptor complexes solubilized by Triton X-100 also led to a rapid dissociation of {sup 125}I-Mel from solubilized ligand-receptor complexes.^Gel filtration chromatography of solubilized ligand-receptor complexes revealed two major peaks of radioactivity corresponding to M{sub r} > 400,000 and M{sub r} ca.^110,000.^This elution profile was markedly altered by pretreatment with GTP({gamma}S) before solubilization; only the M{sub r} 110,000 peak was present in GTP({gamma}S)-pretreated membranes.^The results strongly suggest that {sup 125}I-mel binding sites in lizard brain are melatonin receptors, with agonist-promoted guanine nucleotide-binding protein (G protein) coupling and that the apparent molecular size of receptors uncoupled from G proteins is about 110,000.
Country of PublicationUnited States
LanguageEnglish
FormatPages: 3882-3886
System Entry Date2001 May 13

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