Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.17 (CaMKII)
 4,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) which catalyzes the phosphorylation of troponin T, phosvitin and casein has been purified over 2000 fold from rabbit skeletal muscle. The partial purification of this new enzyme, designated troponin T kinase, involves precipitation of contaminating proteins at pH 6.1, fractionation of the supernatant with (NH4)2SO4 and successive column chromatographies on DEAE-cellulose, hydroxyapatite and Sepharose 6B. The chromatographic patterns on DEAE-cellulose and hydroxyapatite columns show two peaks of troponin T kinase activity. Gel filtration experiments indicate the existence of multiple, possibly aggregated, forms of the enzyme. The purified enzyme does not catalyze the phosphorylation of phosphorylase b, troponin I, troponin C, tropomyosin, protamine, or myosin light chain 2 nor does it catalyze the interconversion of glycogen synthase I into the D form. Troponin T kinase is not affected by the addition of cyclic nucleotides or AMP to the reaction mixture. Divalent cations (other than Mg2+, required for the reaction) do not stimulate the enzyme, and several are inhibitory. Other characteristics of the reaction catalyzed by troponin T kinase, such as Km values for ATP and substrate proteins, pH optima, effect of the concentration of Mg2+, substitution of ATP for GTP have also been studied.
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PMID:Purification and properties of troponin T kinase from rabbit skeletal muscle. 3 14

Two cyclic nucleotide-independent protein kinases (ATP:protein phosphotransferase, EC 2.7.1.37) have been purified to homogeneity from rat liver nuclei. While these enzymes have many similar catalytic properties (preference for acid rather than basic proteins), they differ in molecular weight and subunit composition. Protein kinase NII will utilize ATP and GTP as phosphate donors while protein kinase NI will only effectively use ATP. Both enzymes reveal an unusual activation by Fe2+.
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PMID:Properties of rat liver nuclear protein kinases. 22 67

To investigate the role of calmodulin in stimulus-secretion coupling in pancreatic acinar cells, we studied the effects of W-7, a calmodulin inhibitor, and KN-62, a specific inhibitor of Ca2+/calmodulin-dependent protein kinase II (Ca2+/CaM kinase II), on amylase secretion from rat pancreatic acini. Calmodulin inhibitor (W-7, 100 microM) and Ca2+/CaM kinase II inhibitor (KN-62, 10 microM) reduced amylase secretion stimulated by cholecystokinin (CCK) or carbachol. W-7 and KN-62 also inhibited amylase secretion stimulated by both calcium ionophore (A23187) and phorbol ester (12-O-tetradecanoylphorbol-13-acetate, TPA). To clarify the role of calmodulin in the interaction of intracellular mediators, pancreatic acini were permeabilized with streptolysin O. Following permeabilization, amylase secretion was stimulated by submicromolar free Ca2+, and this Ca(2+)-dependent amylase secretion was enhanced by guanosine 5'-[gamma-thio]triphosphate (GTP gamma S), TPA or cyclic adenosine 3',5'-monophosphate (cAMP). W-7 and KN-62 had no effects on amylase secretion stimulated by Ca2+ alone, but inhibited the enhancement in Ca(2+)-dependent amylase secretion by GTP gamma S, TPA or cAMP. These data suggest that calmodulin plays an important role in Ca(2+)-dependent amylase secretion from pancreatic acinar cells and in the interaction between Ca2+ and other intracellular messengers.
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PMID:Effects of calmodulin inhibitors on amylase secretion from rat pancreatic acini. 128 79

To probe for the involvement of Ca2+/calmodulin-dependent protein kinase II in the regulation of insulin secretion, the effects of a specific inhibitor of this enzyme, KN-62, on secretagogue-stimulated insulin secretion, cytosolic Ca2+ concentration ([Ca2+]i) rise, membrane depolarization, and nutrient metabolism were examined in HIT-T15 cells. KN-62 dose-dependently inhibited insulin secretion induced by a nutrient mixture (10 mM glucose, 5 mM leucine, and 5 mM glutamine) alone or combined with either the Ca(2+)-mobilizing receptor agonist bombesin or the cAMP-raising agent forskolin in intact cells. KN-62 did not affect Ca(2+)- or GTP analogue-induced insulin secretion from permeabilized cells, indicating an action at a step before exocytosis. The stimulating effects of nutrients on insulin secretion, [Ca2+]i, and membrane depolarization were potentiated by bombesin. Similarly, bombesin promoted a larger depolarization and [Ca2+]i rise in the presence of nutrients. This was associated with enhanced Ca2+ mobilization and the appearance of sustained [Ca2+]i elevation. The bombesin-induced membrane depolarization, like the nutrient effect, was inhibited by diazoxide, suggesting that this is due to closure of ATP-sensitive K+ channels. Bombesin elicited Ca2+ influx by both membrane potential-sensitive and -insensitive conductance pathways. KN-62 did not affect Ca2+ mobilization and only partially reduced Ca2+ entry during the sustained [Ca2+]i rise in bombesin-stimulated cells. When added before or during the stimulation, KN-62 dose-dependently inhibited nutrient- and KCl-stimulated [Ca2+]i elevation and Mn2+ influx (reflecting Ca2+ entry). The calmodulin antagonist CGS 9343B and the L-type Ca2+ channel blocker SR-7037 mimicked the inhibitory effect of KN-62 on stimulated insulin secretion and [Ca2+]i elevation. Membrane depolarization and nutrient metabolism (reduction of a tetrazolium derivative), however, were not altered by KN-62 treatment, indicating that the early coupling events from nutrient metabolism to closure of ATP-sensitive K+ channels remain operative. These results suggest that KN-62 and the calmodulin antagonist CGS 9343B inhibit Ca2+ influx by means of direct interaction with L-type Ca2+ channels, which, in turn, causes inhibition of stimulated insulin secretion. Thus, it appears that Ca2+/calmodulin-dependent protein kinase II is not involved in the regulation of insulin secretion.
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PMID:Inhibition of voltage-gated Ca2+ channels and insulin secretion in HIT cells by the Ca2+/calmodulin-dependent protein kinase II inhibitor KN-62: comparison with antagonists of calmodulin and L-type Ca2+ channels. 132 47

The mitogenic neuropeptides bombesin and vasopressin markedly increased tyrosine and serine phosphorylation of multiple substrates in quiescent Swiss 3T3 fibroblasts, including two major bands of Mr 90,000 and 115,000. Tyrosine phosphorylation of these proteins was increased as judged by immunoprecipitation of 32Pi-labeled cells and immunoblotting of unlabeled cells with monoclonal antiphosphotyrosine antibodies, elution with phenyl phosphate, and phospho amino acid analysis. Phosphotyrosyl proteins generated by bombesin and vasopressin did not correspond either by apparent molecular weight or by immunological and biochemical criteria to several known tyrosine kinase substrates, including phospholipase C gamma, the microtubule-associated protein 2 kinase, GTPase-activating protein, or phosphatidylinositol kinase. The effect was rapid (within seconds), concentration dependent, and inhibited by specific receptor antagonists for both bombesin and vasopressin. The endothelin-related peptide, vasoactive intestinal contractor, also elicited a rapid and concentration-dependent tyrosine/serine phosphorylation of a similar set of substrates. These results demonstrate that neuropeptides, acting through receptors linked to GTP-binding proteins, stimulate tyrosine phosphorylation of a common set of substrates in quiescent Swiss 3T3 cells and suggest the existence of an additional signal transduction pathway in neuropeptide-induced mitogenesis.
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PMID:Bombesin, vasopressin, and endothelin rapidly stimulate tyrosine phosphorylation in intact Swiss 3T3 cells. 164 10

A neuron-specific Ca2+/calmodulin-dependent protein kinase, CaM kinase Gr, phosphorylates selectively a Ras-related GTP-binding protein (Rap-1b) that is enriched in brain tissue. The phosphorylation reaction achieves a stoichiometry of about 1 and involves a serine residue near the carboxyl terminus of the substrate. Both CaM kinase Gr and cAMP-dependent protein kinase, but not CaM kinase II, phosphorylate identical or contiguous serine residues in Rap-1b. The rate of phosphorylation of Rap-1b by CaM kinase Gr is enhanced following autophosphorylation of the protein kinase. Other low molecular weight GTP-binding proteins belonging to the Ras superfamily, including Rab-3A, Rap-2b, and c-Ha-ras p21, are not phosphorylated by CaM kinase Gr. The phosphorylation of Rap-1b itself can be reversed by an endogenous brain phosphoprotein phosphatase. These observations provide a potential connection between a neuronal Ca2(+)-signaling pathway and a specific low molecular weight GTP-binding protein that may regulate neuronal transmembrane signaling, vesicle transport, or neurotransmitter release.
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PMID:Phosphorylation of a Ras-related GTP-binding protein, Rap-1b, by a neuronal Ca2+/calmodulin-dependent protein kinase, CaM kinase Gr. 190 12

Several studies suggest that protein kinase C and type II Ca2+/calmodulin-dependent protein kinase are activated during induction of long-term potentiation (LTP). We now report that casein kinase II (CK-II), which is present in high concentration in the hippocampus, is also activated in the CA1 region during LTP. CK-II activity increased within 2 min after a train of high-frequency electrical stimulations and reached a maximum (2-fold increase) 5 min later before returning to baseline value. The stimulated protein kinase activity, which was blocked by a selective antagonist of N-methyl-D-aspartate receptors, exhibited specific properties of CK-II, including phosphorylation of the specific substrates of CK-II, marked inhibition by a low heparin concentration, and the use of GTP as a phosphate donor. CK-II activity was also selectively and rapidly augmented in another form of LTP produced by bath application of tetraethylammonium; this LTP (called LTPk) is Ca2+ dependent but N-methyl-D-aspartate independent. Phosphorylation of casein that was not inhibited by heparin (i.e., casein kinase I) remained unchanged. We suggest that an increase in CK-II activity is important in LTP induction.
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PMID:Rapid activation of hippocampal casein kinase II during long-term potentiation. 194 43

The accessibility of three amino acids of EF-2, located within highly conserved regions near the N- and C-terminal extremities of the molecule (the E region and the ADPR region, respectively) to modifying enzymes has been compared within nucleotide-complexed EF-2 and ribosomal complexes that mimic the pre- and posttranslocational ones: the high-affinity complex (EF-2)-nonhydrolysable GTP analog GuoPP[CH2]P ribosome and the low-affinity (EF-2)-GDP-ribosome complex, EF-2 and ribosomes being from rat liver. We studied the reactivity of two highly conserved residues diphthamide-715 and Arg-66, to diphtheria-toxin-dependent ADP-ribosylation and trypsin attack, and of a threonine that probably lies between residues 51 and 60, to phosphorylation by a Ca2+/calmodulin-dependent protein kinase. Diphthamide 715 and this threonine residue were unreactive within the high-affinity complex but seemed fully reactive in the low-affinity complex. Arg-66 was resistant to trypsin in both complexes. The possible involvement of the E and ADPR regions of EF-2 in the interaction with ribosome in the two complexes is discussed.
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PMID:Modification of the reactivity of three amino-acid residues in elongation factor 2 during its binding to ribosomes and translocation. 232 78

Caldesmon, a major actin- and calmodulin-binding protein of smooth muscle, has been implicated in regulation of the contractile state of smooth muscle. The isolated protein can be phosphorylated by a co-purifying Ca2+/calmodulin-dependent protein kinase, and phosphorylation blocks inhibition of the actomyosin ATPase by caldesmon [Ngai & Walsh (1987) Biochem. J. 244, 417-425]. We have examined the phosphorylation of caldesmon in more detail. Several lines of evidence indicate that caldesmon itself is a kinase and the reaction is an intermolecular autophosphorylation: (1) caldesmon (141 kDa) and a 93 kDa proteolytic fragment of caldesmon can be separated by ion-exchange chromatography: both retain caldesmon kinase activity, which is Ca2+/calmodulin-dependent; (2) chymotryptic digestion of caldesmon generates a Ca2+/calmodulin-independent form of caldesmon kinase; (3) caldesmon purified to electrophoretic homogeneity retains caldesmon kinase activity, and elution of enzymic activity from a fast-performance-liquid-chromatography ion-exchange column correlates with caldesmon of Mr 141,000; (4) caldesmon is photoaffinity-labelled with 8-azido-[alpha-32P]ATP; labelling is inhibited by ATP, GTP and CTP, indicating a lack of nucleotide specificity; (5) caldesmon binds tightly to Affi-Gel Blue resin, which recognizes proteins having a dinucleotide fold. Autophosphorylation of caldesmon occurs predominantly on serine residues (83.3%), with some threonine (16.7%) and no tyrosine phosphorylation. Autophosphorylation is site-specific: 98% of the phosphate incorporated is recovered in a 26 kDa chymotryptic peptide. Complete tryptic/chymotryptic digestion of this phosphopeptide followed by h.p.l.c. indicates three major phosphorylation sites. Caldesmon exhibits a high degree of substrate specificity: apart from autophosphorylation, brain synapsin I is the only good substrate among many potential substrates examined. These observations indicate that caldesmon may regulate its own function (inhibition of the actomyosin ATPase) by Ca2+/calmodulin-dependent autophosphorylation. Furthermore, caldesmon may regulate other cellular processes, e.g. neurotransmitter release, through the Ca2+/calmodulin-dependent phosphorylation of other proteins such as synapsin I.
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PMID:Autophosphorylation of smooth-muscle caldesmon. 341 67

Purified brain tubulin subjected to an exhaustive phosphatase treatment can be rephosphorylated by casein kinase II. This phosphorylation takes place mainly on a serine residue, which has been located at the carboxy-terminal domain of the beta-subunit. Interestingly, tubulin phosphorylated by casein kinase II retains its ability to polymerize in accordance with descriptions by other authors of in vivo phosphorylated tubulin. Moreover, the V8 phosphopeptide patterns of both tubulin phosphorylated in vitro by casein kinase II and tubulin phosphorylated in vivo in N2A cells are quite similar, and different from that of tubulin phosphorylated in vitro by Ca/calmodulin-dependent kinase II. On the other hand, we have found an endogenous casein kinase II-like activity in purified brain microtubule protein that uses GTP and ATP as phosphate donors, is inhibited by heparin, and phosphorylates phosphatase-treated tubulin. Thus it appears that a casein kinase II-like activity should be considered a candidate for the observed phosphorylation of beta-tubulin in vivo in brain or neuroblastoma cells.
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PMID:Tubulin phosphorylation by casein kinase II is similar to that found in vivo. 347 37


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