title: Photoaffinity labelling of Ca2+ channels with [3H]azidopine.
abstract: A 1,4-dihydroypyridine arylazide photoaffinity ligand, [3H]azidopine (50.6 Ci/mmol), has been synthesized. [3H]Azidopine binds reversibly with a Kd of 350 pM to guinea-pig skeletal muscle membranes in the absence of ultraviolet light. The reversible [3H]azidopine binding is inhibited steroselectively by 1,4-dihydropyridines, phenylalkylamine Ca2+ channel blockers and La3+. Covalent incorporation into membrane proteins after photolysis was investigated by sodium dodecyl sulfate polyacrylamide slab gel electrophoresis. [3H]Azidopine is photoincorporated specifically into a protein of Mr approximately 145 000. The covalent labelling of the Mr approximately 145 000 band is inhibited stereoselectively by drugs and cations which block the reversible [3H]azidopine binding. It is suggested that [3H]azidopine is photoincorporated into a subunit of the putative Ca2+ channel.
mesh_terms: D000345:Affinity Labels / Q000378:metabolism; D000818:Animals; D001386:Azides / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D004095:Dihydropyridines; D006168:Guinea Pigs; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D009132:Muscles / Q000378:metabolism*; D010782:Photolysis; D011725:Pyridines / Q000378:metabolism*; D014316:Tritium
chemical_list: D000345:Affinity Labels; D001386:Azides; D002121:Calcium Channel Blockers; D004095:Dihydropyridines; D007473:Ion Channels; D011725:Pyridines; D014316:Tritium; C041130:azidopine; D002118:Calcium