Purification of the opiate receptor from rat brain.

Abstract

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-.beta.-bromoacetamidomorphine, a newly synthesized ligand, to .omega.-aminohexyl-Sepharose. After elution of the nonspecific proteins with 50 mM Tris (pH 7.5), the receptor proteins were eluted with 1 .mu.M levorphanol or etorphine. NaDodSO4[sodium dodecyl sulfate]/polyacrylamide gel electrophoresis revealed 3 major proteins associated with the opiate receptor, having MW of 43,000, 35,000 and 23,000. The purified receptor binds 10-11 mol of dihydromorphine/mg of protein, with a Kd of 3.8 .times. 10-9 M. Other opiates, naloxone and methionine-enkephalin inhibit [3H]dihydromorphine binding in a manner similar to that observed with intact and solubilized neural membranes.