MOUSE-BRAIN OPIOID RECEPTOR IDENTIFICATION BY DIRECT ULTRAVIOLET PHOTOAFFINITY-LABELING

[H-3]Morphine, PL-017[prolyl-3,4-H-3,D-prolyl,3,4-H-3] ([H-3]PL-017) a nd -penicillamine,5-D-penicillamine)[tyrosyl-2,6-H-3] ([H-3]DPDPE) wer e directly cross-linked to mouse brain opiate receptors by an ultravio let (254 nm) irradiation procedure. [H-3]Morphine preferentially and s pecifically labeled a 58 kDa protein. The labeling of this protein was suppressed by the addition of excess naloxone. Dithiothreitol reduced the irreversible binding of [H-3]morphine and [H-3]PL-017 to the rece ptor protein. In the acid hydrolysate of [H-3]DPDPE-labeled opiate rec eptors, dityrosine, was detected. These results suggest that the [H-3] tyrosine residue of [H-3]DPDPE covalently bound the tyrosine residue o f delta-opioid receptors. The direct UV-photoaffinity labeling method using commercially available radioactive opiates described here should be a useful tool for characterization and purification of the opiate receptors.