Abstract
An opioid binding protein (OBP) purified to homogeneity from bovine striatal membranes was reconstituted into liposomes. For most experiments a CHAPS extract of bovine striatum, devoid of opioid binding, served as source of G-proteins and lipids. Liposomes were formed by precipitation of a mixture of OBP and CHAPS extract with polyethylene glycol-6000 (PEG). Reconstituted OBP bound μ agonist ligands stereos-pecifically and with high affinity, similar to that of membrane-bound μ-receptors. The binding was highly selective for μ-ligands, as compared to δ and κ-ligands and was completely inhibited by GTPγS. Similar results were obtained in reconstitution experiments with purified G-proteins. Stimulation of low Km GTPase by μ-agonists was observed. These results indicate that recoupling of purified receptor with G protein has taken place in this system and confirm that OBP is a μ binding protein.
Published Version
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