The human dopamine D2S receptor was expressed in the methylotrophic yeast Pichia pastoris, where the receptor with a molecular mass of approximately 40 kDa exhibited specific and saturable binding properties. The dopamine antagonist [H-3]spiperone showed an average dissociation constant K-d of 0.6 +/- 0.17 nM for the dopamine D2S receptor. The receptor was solubilized using the non-ionic detergent dodecylmaltoside and purified by affinity chromatography using a Ni2+ chelate (His-Trap) column or by batch extraction with an anti-FLAG M1 affinity resin. The receptor maintained its biological activity after solubilization and purification from the membrane protein fraction. A 244- or 185-fold enrichment, as judged by an increase in specific binding, was obtained after adsorption to the His-Trap or anti-FLAG materials, respectively. (C) 2003 Elsevier Inc. All rights reserved.