title: Phosphorylation of the 1,4-dihydropyridine receptor of the voltage-dependent Ca2+ channel by an intrinsic protein kinase in isolated triads from rabbit skeletal muscle.
abstract: Isolated triads from rabbit skeletal muscle were shown to contain an intrinsic protein kinase which was neither Ca2+/calmodulin-dependent nor cAMP-dependent. The protein substrates phosphorylated by this protein kinase exhibited apparent molecular weights of 300,000, 170,000, 90,000, 80,000, 65,000, 56,000, 52,000, 51,000, 40,000, 25,000, 22,000, and 15,000. Purification of the 1,4-dihydropyridine receptor from phosphorylated triads has demonstrated that the 170,000- and 52,000-Da subunits of the 1,4-dihydropyridine receptor are phosphorylated by this intrinsic protein kinase in isolated triads. Monoclonal antibodies to the 170,000-Da subunit of the dihydropyridine receptor immunoprecipitated the 170,000-Da phosphoprotein from detergent extracts of phosphorylated triads. The mobility of the 170,000-Da phosphoprotein in sodium dodecyl sulfate-polyacrylamide gels was not changed with or without reduction, demonstrating that the 170,000-Da phosphoprotein is not the glycoprotein subunit of the receptor. Our results demonstrate that the 170,000- and 52,000-Da subunits of the dihydropyridine receptor are phosphorylated by an intrinsic protein kinase in isolated triads. In addition, our results also demonstrate that the 175,000-Da glycoprotein subunit of the dihydropyridine receptor is not phosphorylated in isolated triads by the intrinsic protein kinase, cAMP-dependent protein kinase, or endogenous Ca2+/calmodulin-dependent protein kinase.
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000378:metabolism; D015220:Calcium Channels; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D009132:Muscles / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits; D011978:Receptors, Nicotinic / Q000302:isolation & purification / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D007473:Ion Channels; D046911:Macromolecular Substances; D011978:Receptors, Nicotinic; D011494:Protein Kinases