Purification of the opiate receptor of NG108-15 neuroblastoma-glioma hybrid cells

Abstract

Opiate receptors from NG108-15 neuroblastoma-glioma hybrid cell membranes were purified to apparent homogeneity in a form covalently labeled with the opiate affinity ligand 3-methylfentanylisothiocyanate (super-FIT). The purification procedure consists of five steps: quantitative labeling of opiate receptors in membranes with super-FIT; solubilization in a lubrol/3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate mixture; adsorption to and elution from a wheat germ agglutinin-Sepharose column; immunoaffinity chromatography on columns of immobilized anti-fentanyl; preparative gel electrophoresis in the presence of NaDodSO4. The protein was purified approximately 30,000-fold in 3% overall yield to a state in which there is 1 mol of super-FIT bound per mol of protein, corresponding to 21,000 pmol per mg of protein, the theoretically expected specific activity. The protein is glycosylated and migrates on NaDodSO4 gel electrophoresis with a Mr near 58,000. It has a strong tendency to dimerize, even in the presence of denaturing detergents, and it exists primarily as an oligomer in nondenaturing detergents.