Melatonin binding proteins identified in the rat brain by affinity labeling.
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-[125I]iodomelatonin binding. In parallel, the radioactive form of BIM, N-bromoacetyl-2-[125I]iodo-5-methoxytryptamine ([125I]BIM) became incorporated into the synaptosomes. The incorporation of [125I]BIM was inhibited by BIM, 2-iodomelatonin and melatonin but not by 5-methoxytryptamine or N-acetyl serotonin. [125I]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.
Laudon
M
M
Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel.
Zisapel
N
N
D000345:Affinity Labels; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002855:Chromatography, Thin Layer; D007700:Kinetics; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives* / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000737:chemistry*
D000345:Affinity Labels; D002352:Carrier Proteins; C044556:2-iodomelatonin; D008550:Melatonin