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Identification of the Subunit Structure of Rat Pineal Adrenergic Receptors by Photoaffinity Labeling
Author(s) -
Dickinson Kenneth E. J.,
LeebLundberg L. M. Fredrik,
Strasser Ruth H.,
Caron Marc G.,
Lefkowitz Robert J.
Publication year - 1986
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1986.tb00630.x
Subject(s) - receptor , photoaffinity labeling , dissociation constant , agonist , peptide , adrenergic receptor , biochemistry , chemistry , protein subunit , biology , medicine , endocrinology , microbiology and biotechnology , stereochemistry , gene
The adrenergic receptors of rat pineal gland were investigated using radiolabeled ligand binding and photoaffinity labeling techniques. 125 I‐2‐[β‐(4‐hydroxyphenyl)ethylaminomethyl]tetralone ( 125 I‐HEAT) and 125 I‐cyanopindolol ( 125 I‐CYP) labeled specific sites on rat pineal gland membranes with equilibrium dissociation constants ( K D ) of 48 (±5) p M and 30 (±5) p M , respectively. Binding site maxima were 481 (±63) and 1,020 (±85) fmol/mg protein. The sites labeled by 125 I‐HEAT had the pharmacological characteristics of α 1 ‐adrenergic receptors. 125 I‐CYP‐labeled β‐adrenergic receptors were characterized as a homogeneous population of β 1 ‐adrenergic receptors. The α 1 ‐ and β 1 ‐adrenergic receptors were covalently labeled with the specific photoaffinity probes 4‐amino‐6,7‐dimethoxy‐2‐{4‐[5‐(4‐azido‐3‐[ 125 I]iodo‐phenyl) pentanoyl]‐1‐piperazinyl}quinazoline ( 125 I‐APDQ) and 125 I‐p‐azidobenzylcarazolol ( 125 I‐pABC). 125 I‐APDQ labeled an α 1 ‐adrenergic receptor peptide of M r = 74,000 (±4,000), which was similar to peptides labeled in rat cerebral cortex, liver, and spleen. 125 I‐pABC labeled a single β 1 ‐adrenergic receptor peptide with a M r = 42,000 (±1,500), which differed from the 60–65,000 peptide commonly seen in mammalian tissues. Possible reasons for these differences are discussed.