Target size analysis of opioid receptors. No difference between receptor types, but discrimination between two receptor states.
Target size analysis of opioid receptor is complicated by the presence of multi-exponential inactivation curves. Irradiation of intact frozen tissue proved essential to eliminate such artifacts, due to indirect irradiation effects. Upon irradiation condition, opioid binding activity was inactivated in a single mono-exponential manner. Identical inactivation curves were obtained for mu, delta and kappa binding activities in brain membranes from rat, guinea-pig and frog and in NG 108-15 cells: the molecular mass obtained was 98 +/- 2 kDa. However, when opioid binding was assayed in the presence of Na+, Mg2+ and GTP, the molecular mass was found to be only 56 +/- 4.4 kDa. We suggest that the opioid recognition site comprises a unit of 56 kDa and that in the absence of Na+, Mg2+ and GTP an additional membrane component of 40-44 kDa is necessary for high-affinity opioid binding.
D000818:Animals; D001923:Brain Chemistry; D002460:Cell Line; D005612:Freeze Drying; D005615:Freezing; D005910:Glioma; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006168:Guinea Pigs; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008970:Molecular Weight; D009447:Neuroblastoma; D011893:Rana esculenta; D051381:Rats; D011957:Receptors, Opioid / Q000032:analysis / Q000528:radiation effects*; D012964:Sodium / Q000494:pharmacology; D013552:Swine; D013570:Synaptic Membranes / Q000378:metabolism / Q000528:radiation effects
D011957:Receptors, Opioid; D006160:Guanosine Triphosphate; D012964:Sodium; D008274:Magnesium