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Melatonin binding proteins identified in the rat brain by affinity labeling
Author(s) -
Laudon Moshe,
Zisapel Nava
Publication year - 1991
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(91)81013-x
Subject(s) - melatonin , synaptosome , incubation , biochemistry , serotonin , covalent bond , chemistry , binding site , biology , endocrinology , in vitro , receptor , organic chemistry
N ‐Bromoacetyl‐2‐iodo‐5‐methoxytryptamine (BIM), a novel derivative of the biologically active melatonin analog, 2‐iodomelatonin, was prepared and used to identify melatonin binding proteins in rat brain synaptosomes. Incubation of the synaptosomes with BIM resulted in a time and concentration dependent, irreversible inhibition of 2‐[ 125 I]iodomelatonin binding. In parallel, the radioactive form of BIM, N ‐bromoacetyl‐2‐[ 125 I]iodo‐5‐methoxytryptamine [ 125 I]BIM) became incorporated into the synaptosomes. The incorporation of [ 125 I]BIM was inhibited by BIM, 2‐iodomelatonin and melatonin but not by 5‐methoxytryptamine or N ‐acetyl serotonin. [ 125 I]BIM became covalently attached to three polypeptides with apparent molecular weight values of 92, 55 and 45 kDa; the labeling of all three proteins was markedly inhibited by melatonin. These results indicate that the 92, 55 and 45 kDa polypeptides are melatonin binding proteins.