Reconstitution of a purified mu-opioid binding protein in liposomes: selective, high affinity, GTP gamma S-sensitive mu-opioid agonist binding is restored.

An opioid binding protein (OBP) purified to homogeneity from bovine striatal membranes has been reconstituted in liposomes. The liposomes were produced by PEG-precipitation of OBP in the presence of a CHAPS extract of bovine striatum, devoid of opioid binding. High affinity mu-agonist binding was restored. The binding was selective for mu-agonists, stereospecific and inhibited by GTP gamma S. These results demonstrate that there is recoupling of OBP with G-protein and confirm our earlier evidence that the purified OBP is a mu-opioid binding site.