부산대학교 도서관

The voltage-dependent calcium channel from guinea-pig skeletal muscle T-tubules has been isolated with a rapid, two-step purification procedure. Reversible postlabelling of the channel-linked 1,4-dihydropyridine receptor and stereoselective photolabelling as a novel approach were employed to assess purity. A 135-fold purification to a specific activity of 1311 ± 194 pmol/mg protein (determined by reversible equilibrium binding with (+)- [³H]PN200-110) was achieved. Three polypeptides of 155 kDa, 65 kDa and 32 kDa were identified in the purified preparation. The 155-kDa band is a glycoprotein. The arylazide photoaffinity probe (-)-[³H]azidopine bound with high affinity to solubilized membranes (Kd = 0.7 ± 0.2 nM) and highly purified fractions (Kd = 3.1 ± 2 nM), whereas the optical antipode (+)-azidopine was of much lower affinity. Irradiation of (-)-[³H]azidopinc and (+)- [³H]azidopinc receptor complexes with ultraviolet light led to preferential incorporation of the (-) enantiomer into the 155-kDa polypeptide in crude solubilized and purified preparations. The pharmacological profile of irreversible labelling of the 155-kDa glycoprotein by (-)-[³H]azidopine is identical to that found in reversible binding experiments. Specific photolabelling of the 155-kDa band by (-)-[³H]azidopine per milligram of protein increases 150-fold upon purification, whereas incorporation into non-specific bands in the crude solubilized material is identical for both, (-) and (+)-[³H]azidopine. [ABSTRACT FROM AUTHOR]