title: Phosphorylation of the purified receptor for calcium channel blockers by cAMP kinase and protein kinase C.
abstract: The dihydropyridine receptor purified from rabbit skeletal muscle contains three proteins of 165, 55 and 32 kDa. cAMP kinase and protein kinase C phosphorylate the 165-kDa and the 55-kDa proteins. At identical concentrations of each protein kinase, cAMP kinase phosphorylates the 165-kDa protein faster than the 55-kDa protein. Protein kinase C phosphorylates preferentially the 55-kDa protein. cAMP kinase incorporates up to 1.6 mol phosphate/mol protein into the 165-kDa protein and 1 mol/mol into the 55-kDa protein upon prolonged incubation. At a physiological concentration of cAMP kinase 1 mol phosphate is incorporated/mol 165-kDa protein within 10 min, suggesting a physiological role of this phosphorylation. Protein kinase C incorporates up to 1 mol phosphate/mol into the 55-kDa protein and less than 1 mol/mol into the 165-kDa protein. Tryptic phosphopeptide analysis reveals that cAMP kinase phosphorylates two distinct peptides in the 165-kDa protein, whereas protein kinase C phosphorylates a single peptide in the 165-kDa protein. cAMP kinase and protein kinase C phosphorylate three and two peptides in the 55-kDa protein, respectively. Mixtures of the tryptic phosphopeptides derived from the 165-kDa and 55-kDa proteins elute according to the composite of the two elution profiles. These results suggest that the 165-kDa protein, which contains the binding sites for each class of calcium channel blockers and the basic calcium-conducting structure, is a specific substrate for cAMP kinase. The 55-kDa protein apparently contains sites preferentially phosphorylated by protein kinase C.
authors.affiliation: Physiologische Chemie, Medizinische Fakultät der Universität des Saarlandes, Homburg/Saar, Federal Republic of Germany.
authors.forename: W
authors.initials: W
authors.lastname: Nastainczyk
authors.forename: A
authors.initials: A
authors.lastname: Röhrkasten
authors.forename: M
authors.initials: M
authors.lastname: Sieber
authors.forename: C
authors.initials: C
authors.lastname: Rudolph
authors.forename: C
authors.initials: C
authors.lastname: Schächtele
authors.forename: D
authors.initials: D
authors.lastname: Marmè
authors.forename: F
authors.initials: F
authors.lastname: Hofmann
mesh_terms: D000818:Animals; D015220:Calcium Channels; D002417:Cattle; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D000242:Cyclic AMP / Q000494:pharmacology*; D007700:Kinetics; D008861:Microsomes / Q000032:analysis; D009132:Muscles / Q000032:analysis; D010446:Peptide Fragments / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D011978:Receptors, Nicotinic / Q000378:metabolism*; D013379:Substrate Specificity; D014357:Trypsin / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D010446:Peptide Fragments; D011978:Receptors, Nicotinic; D000242:Cyclic AMP; D011494:Protein Kinases; D011493:Protein Kinase C; D014357:Trypsin