Solubilization and partial purification of the high affinity [ 3H] imipramine binding site from human platelets

Abstract

Several lines of evidence have suggested that this site is structurally related to the uptake site for serotonin and that high affinity [3H]imipramine binding can serve as a label of the serotonin transporter [4-71. In order to determine the molecular properties of the high affinity [3H]im- ipramine binding site and further characterize its structural relationship to the serotonin transporter, we initiated a series of experiments to solubilize and subsequently purify the binding site from human platelet membranes. The present report describes the solubilization of the [3H]imipramine binding site from human platelets. The solubilized binding site has a pharmacological profile and ca- tion requirement which is identical to the membrane-bound binding site. Optimal solubiliza- tion was achieved using the detergent 3-[(3-chol- amidopropyl)dimethylammonio] - 1 -propanesulfo- nate (CHAPS) which is a zwitterionic derivative of cholic acid that has been successfully used for solubilization of other receptors [8, lo]. Partial purification of the solubilized [3H]imipramine bin- ding site was carried out by gel filtration chromato- +