Affinity labeling of melatonin binding sites in the hamster brain.
N-Bromoacetyl-2-iodo-5-methoxytryptamine (BIM), a novel derivative of the biologically active melatonin analog, 2-iodomelatonin, was used to identify melatonin binding proteins in synaptosomes from Syrian hamster brain. Incubation of the synaptosomes with BIM resulted in a concentration dependent, irreversible inhibition of 2-125I-iodomelatonin binding. The radioactive form of BIM, N-Bromoacetyl-2-125I-iodo-5-methoxytryptamine (125I-BIM), became covalently attached to three proteins in the synaptosomes, in a concentration dependent manner. These proteins had apparent molecular weight values of 92, 55 and 45 kilodaltons. The incorporation of 125I-BIM into all three proteins was inhibited by BIM greater than 2-iodomelatonin greater than melatonin whereas the melatonin antagonist N-(1,4 dinitrophenyl)- 5-methoxytryptamine (ML-23) selectively inhibited the labeling of the 45 kDa protein. These results indicate that the 92, 55 and 45 KDa polypeptides are melatonin binding proteins.
Anis
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Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel.
Zisapel
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D008735:5-Methoxytryptamine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D006224:Cricetinae; D007700:Kinetics; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D008647:Mesocricetus; D044094:Receptors, Melatonin; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism
D044094:Receptors, Melatonin; D017981:Receptors, Neurotransmitter; C070373:N-bromoacetyl-2-iodo-5-methoxytryptamine; D008735:5-Methoxytryptamine; D008550:Melatonin