Purification of the Opiate Receptor from Rat Brain

The opiate receptor was purified from a Triton-solubilized preparation of rat neural membranes by the use of affinity chromatography. The affinity gel was prepared by coupling 14-β -bromoacetamidomorphine, a newly synthesized ligand, to ω -aminohexyl-Sepharose. After elution of the nonspecific proteins with 50 mM Tris (pH 7.5), the receptor proteins were eluted with 1 μ M levorphanol or etorphine. NaDodSo4/polyacrylamide gel electrophoresis revealed three major proteins associated with the opiate receptor, having molecular weights of 43,000, 35,000, and 23,000. The purified receptor binds 10-11mol of dihydromorphine/per mg of protein, with Kdof 3.8× 10-9M. Other opiates, naloxone, and methionine-enkephalin, inhibit [3H] dihydromorphine binding in a manner similar to that observed with intact and solubilized neural membranes.