gamma-Aminobutyric acid and benzodiazepine receptors: copurification and characterization.

gamma-Aminobutyric acid (GABA) and benzodiazepine receptors have been solubilized and purified by procedures such as gel filtration, ion-exchange, lectin, and affinity chromatographies. All of these procedures enhance the specific activity of each receptor to a similar extent. The drug specificities of [3H]muscimol and [3H]flunitrazepam binding sites are the same after extensive purification by affinity chromatography compared to the membrane bound and initially solubilized receptors. GABA and chloride stimulation of benzodiazepine binding is retained in pure receptors. Two bands are covalently labeled with [3H]flunitrazepam after ultraviolet irradiation of the purified receptor. The persistent association of GABA, benzodiazepine, and chloride recognition sites after extensive purification suggests that they may be part of a single macromolecular complex.