title: Photoaffinity labelling of the Ah receptor.
abstract: A series of halodibenzo-p-dioxins bearing the arylazide photolabile functional group were synthesized and tested as photoaffinity labels for the Ah receptor. 2-Azido-3-iodo-7,8-dibromodibenzo-p-dioxin (KD = 0.76 X 10(-9) M) was selected for radiosynthesis. Analysis of the 125I-photoaffinity-labelled proteins in mouse-liver cytosol by denaturing gel electrophoresis revealed two peptides which had apparent molecular masses of 95,000 and 70,000 daltons respectively, were labelled in an approximately 1:1 ratio and were selectively labelled at low concentrations of the photoaffinity ligand (0.05 KD = 0.04 X 10(-9) M). In addition, their labelling was inhibited by co-incubation with an excess of unlabelled ligand. On chromatographic separation under non-denaturing conditions, these two peptides co-migrated. These studies suggest that the Ah receptor in mouse liver cytosol is a heterodimer composed of two non-covalently bound peptides (95 K and 70 K) which each have a ligand binding site.
mesh_terms: D000345:Affinity Labels / Q000378:metabolism*; D000818:Animals; D003600:Cytosol / Q000378:metabolism; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D051379:Mice; D008810:Mice, Inbred C57BL; D008970:Molecular Weight; D010777:Photochemistry; D000072317:Polychlorinated Dibenzodioxins / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug / Q000032:analysis* / Q000378:metabolism; D013329:Structure-Activity Relationship; D014316:Tritium
chemical_list: D000345:Affinity Labels; D007457:Iodine Radioisotopes; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug; D014316:Tritium