title: A novel, calcium-inhibitable casein kinase in Paramecium cells.
abstract: This is the first identification of a Ca2+-inhibitable casein kinase (CPK) which we have isolated from the 100000 x g supernatant of Paramecium cell homogenates. The 1000-fold enriched CPK activity depends on millimolar Mg2+ and is inhibited by low concentrations of heparin or by > or = 100 microM Ca2+. Enzyme activity is stimulated by polylysine or polyarginine with either casein or with specific casein kinase-2 (CK-2) peptide substrates (RRRDDDSDDD and RREEETEEE). The enzymic properties are similar with GTP instead of ATP. CPK does not undergo autophosphorylation. In gel kinase assays, enzyme activity is associated with a 36 kDa band. Calmodulin as another characteristic substrate for mammalian CK-2 has not been phosphorylated by this protein kinase. Besides casein, CPK phosphorylates in vitro the catalytic subunit of bovine brain calcineurin (CaN), a typical substrate of type 1 mammalian casein kinase (CK-1) in vitro. Again this phosphorylation is significantly reduced by Ca2+. Thus, CPK combines aspects of different casein kinases, but it is clearly different from any type known by its Ca2+ inhibition. Since CPK also phosphorylates the exocytosis-sensitive phosphoprotein, PP63, in Paramecium, which is known to be dephosphorylated by CaN, an antagonistic Ca2+-effect during phosphorylation/dephosphorylation cycles may be relevant for exocytosis regulation.
authors.affiliation: Faculty of Biology, University of Konstanz, Germany. Roland.Kissmehl@uni-konstanz.de
authors.forename: R
authors.initials: R
authors.lastname: Kissmehl
authors.forename: T
authors.initials: T
authors.lastname: Treptau
authors.forename: K
authors.initials: K
authors.lastname: Hauser
authors.forename: H
authors.initials: H
authors.lastname: Plattner
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D019703:Calcineurin; D002118:Calcium / Q000494:pharmacology*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D047388:Casein Kinases; D002413:Cations, Divalent / Q000494:pharmacology; D002417:Cattle; D002846:Chromatography, Affinity; D002848:Chromatography, DEAE-Cellulose; D002852:Chromatography, Ion Exchange; D004533:Egtazic Acid / Q000494:pharmacology; D007700:Kinetics; D009842:Oligopeptides; D016805:Paramecium tetraurelia / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D002148:Calmodulin-Binding Proteins; D002413:Cations, Divalent; D009842:Oligopeptides; D004533:Egtazic Acid; D011494:Protein Kinases; D047388:Casein Kinases; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D002118:Calcium