Sulfhydryl group(s) in the ligand binding site of the D-1 dopamine receptor: specific protection by agonist and antagonist

Journal Article · Tue Oct 21 04:00:00 EDT 1986 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00369a055· OSTI ID:6616171

Sidhu, A; Kassis, S; Kebabian, J; Fishman, P H

An iodinated compound, (/sup 125/I)-8-iodo-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepin-7-ol, has been recently reported to be a specific ligand for the D-1 dopamine receptor. Due to its high affinity and specific activity, this ligand was chosen for the biochemical characterization of the D-1 receptor. Alkylation of particulate fractions of rat caudate nucleus by N-ethylmaleimide (NEM) caused an inactivation of the D-1 receptor, as measured by diminished binding of the radioligand to the receptor. The inactivation of the receptor sites by NEM was rapid and irreversible, resulting in a 70% net loss of binding sites. On the basis of Scatchard analysis of binding to NEM-treated tissue, the loss in binding sites was due to a net decrease in the receptor number with a 2-fold decrease in the affinity of the receptor for the radioligand. Receptor occupancy by either a D-1 specific agonist or antagonist protected the ligand binding sites from NEM-mediated inactivation. NEM treatment of the receptor in the absence or presence of protective compound abolished the agonist high-affinity state of the receptor as well as membrane adenylate cyclase activity. The above-treated striatal membranes were fused with HeLa membranes and assayed for dopamine-stimulated adenylate cyclase activity. When the sources of D-1 receptors were from agonist-protected membranes, the receptors retained the ability to functionally couple to the HeLa adenylate cyclase. These results suggest that the D-1 dopamine receptor contains NEM-sensitive sulfhydryl group(s) either at or near the vicinity of the ligand binding sites, which are critical for both receptor binding and function.

• Research Organization: National Institutes of Health, Bethesda, MD
• OSTI ID: 6616171
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 25:21; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
AMINES
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
BETA DECAY RADIOISOTOPES
BODY
BRAIN
CARDIOTONICS
CARDIOVASCULAR AGENTS
CENTRAL NERVOUS SYSTEM
CYCLASES
DAYS LIVING RADIOISOTOPES
DOPAMINE
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
HELA CELLS
HYDROXY COMPOUNDS
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGANDS
LYASES
MAMMALS
MEMBRANE PROTEINS
MOLECULAR STRUCTURE
NERVOUS SYSTEM
NEUROREGULATORS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
ORGANS
PHENOLS
POLYPHENOLS
PROTEINS
RADIOISOTOPES
RADIORECEPTOR ASSAY
RATS
RECEPTORS
RODENTS
SYMPATHOMIMETICS
TRACER TECHNIQUES
VERTEBRATES