title: Identification of an opioid receptor subunit carrying the mu binding site.
abstract: The enkephalin affinity reagent [3H]Tyr-D-Ala-Gly-Phe-Leu-CH2Cl [( 3H]DALECK) was synthesized. It exhibited high-affinity reversible binding, at pH 7.4, to both mu and delta opioid receptor sites in rat brain membranes. At pH 8.1, nanomolar levels of [3H]DALECK produced an irreversible labeling in synaptic membranes, essentially only in one subunit of 58 000 daltons. The irreversible phase of the reaction reduced the subsequent binding of a mu-selective enkephalin derivative but not that of a delta-selective one. It is concluded that a mu subunit of the opioid receptor exists, can be alkylated specifically, and is of Mr 58 000.
mesh_terms: D000345:Affinity Labels / Q000378:metabolism; D000478:Alkylation; D000590:Amino Acid Chloromethyl Ketones / Q000138:chemical synthesis / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000378:metabolism; D016308:Enkephalin, Leucine-2-Alanine; D004745:Enkephalins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D008970:Molecular Weight; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism*; D013570:Synaptic Membranes / Q000378:metabolism
chemical_list: D000345:Affinity Labels; D000590:Amino Acid Chloromethyl Ketones; D004745:Enkephalins; D011957:Receptors, Opioid; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004743:Enkephalin, Leucine; D016308:Enkephalin, Leucine-2-Alanine; C028557:tyrosyl-alanyl-glycyl-phenylalanyl-leucine chloromethyl ketone