Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The endogenous protein-phosphorylating activity of isolated chromatin was tested. We have found that a group of high-molecular-weight proteins (Mr greater than 50 000) was preferentially phosphorylated when chromatin from mouse ascites cells or from bovine lymphocytes was incubated in the presence of ATP. After disintegration of chromatin by nuclease treatment or by high salt concentration, a larger spectrum of chromatin proteins becomes accessible for phosphorylation by the chromatin-bound protein kinase. Some observations described in this communication may help to partially explain this result. The protein kinase was not found in nucleosomal subunits, indicating a non-random distribution of the enzyme in chromatin. This suggests that enzyme and substrate have to be in close spatial contact for the phosphorylation reaction to occur. Furthermore, we have shown for one protein, histone H1, that phosphorylation sites for the endogenous protein kinase are available on the free but not on the DNA-bound protein, suggesting that phosphate-accepting sites in chromatin proteins may be blocked by protein-DNA or by protein-protein interactions. We also discuss the possibility that chromatin protein kinase occurs in stable complexes with its phosphate-accepting substrates, as has been suggested by the findings of other [Kish, V.M. & Kleinsmith, L.J. (1974) J. Biol. Chem. 249, 750-760].
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PMID:Studies on protein-phosphorylation reactions in isolated chromatin. 19 26

The high-affinity binding site for ATP of the holoenzyme of cAMP-dependent protein kinase (type I) from rabbit skeletal muscle has been investigated. Binding affinity of a series of ATP derivatives substituted at different sites in the molecule was determined by competition with tritiated ATP. The results were compared with data available from cAMP derivatives with the same substituents, in order to analyse the electronic and steric features of these two sites on the protein kinase. The comparison revealed significant differences of the effect of substituents towards the two sites. In particular the N6-derivatives of ATP and substituents affecting the gamma-phosphate indicate that the high-affinity ATP site of the protein kinase has similar properties as those found for phosphotransferase sites. The present results are consistent with the supposition that the high-affinity site for ATP on the holoenzyme is congruent with the phosphotransferase site of the catalytic subunit. Upon combination of catalytic and regulatory subunits this site would be transformed into a high-affinity site for ATP with simultaneous blocking of the phosphotransferase activity.
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PMID:Mechanism of activation of the protein kinase I from rabbit skeletal muscle. The high-affinity ATP site of the holoenzyme. 20 Apr 26

A cAMP-independent protein kinase from chicken liver phosphorylated and inactivated pyruvate kinase type M2 from the same tissue. Complete inactivation was reached when 4 mol of phosphate were incorporated/mol of tetrameric pyruvate kinase. The protein kinase bound with high affinity to pyruvate kinase type M2 (Km value for pyruvate kinase = 6 X 10(-10)M; it phosphorylated phosvitin and casein but not histones, ATP and GTP were substrates. The differences between the properties of this protein kinase in the interconversion of pyruvate kinase and that described previously are discussed.
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PMID:Inactivation of pyruvate kinase type M2 from chicken liver by phosphorylation, catalyzed by a cAMP-independent protein kinase. 20 May 42

Synthetic polypeptides were employed as substrates in kinetic analyses of the reaction mechanism for the catalytic subunit of a cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) from calf thymus. This enzyme preparation was shown to catalyze the transfer of phosphate from ATP to histone H1 from calf thymus, as well as to two synthetic polypeptides, Arg-Lys-Ala-Ser-Gly-Pro (H1-6) and Arg-Arg-Lys-Ala-Ser-Gly-Pro (H1-7), corresponding to the amino acid sequence about serine-38 in calf H1. A related, basic heptapeptide corresponding to a sequence from pig liver pyruvate kinase, Leu-Arg-Arg-Ala-Ser-Leu-Gly (K), was also a substrate. The stoichiometry of peptide phosphorylation was established in each case as the transfer of 1 mol of phosphate from the gamma position of MgATP to the serine hydroxyl of 1 mol of the peptide. Steady-state, initial-velocity, kinetic parameters were determined for each substrate, using various concentrations of ATP. Under the conditions used, all synthetic peptides reacted with greater maximum velocities than whole histone H1. Nevertheless, the K(m) for H1, 54 muM, was lower than the K(m) values of the synthetic substrates. The most efficient substrate was peptide K, which had a V(max) of 50.6 mumol/min per mg of kinase and a K(m) of 63 muM. In the absence of peptide substrate no ATPase activity was detectable at a sensitivity of 0.05% of the rate of peptide phosphorylation, suggesting that ATP is not cleaved to form an unstable phosphoenzyme complex. The data are consistent with a sequential reaction mechanism involving a ternary complex between enzyme, polypeptide substrate, and ATP.
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PMID:Studies on the mechanism of phosphorylation of synthetic polypeptides by a calf thymus cyclic AMP-dependent protein kinase. 20 Sep 11

Incorporation of 32P from [gamma-32P]ATP into a homogenous preparation of rat hepatic fructose-1,6-bisphosphatase (D-fructose-1,6-bisphosphatase 1-phosphohydrolase, EC 3.1.3.11) was catalyzed by a homogeneous preparation of the catalytic subunit of cyclic AMP-dependent protein kinase from bovine liver. Approximately 4 mol of phosphate were incorporated per mol of the tetrameric enzyme. This phosphorylation was associated with an increase in enzyme activity. In addition, in vivo phosphorylation of the enzyme was observed after injection of radioactive inorganic phosphate into rats and subsequent isolation of the enzyme by conventional purification methods and by immunoprecipitation. All of the labeled phosphate incorporation into the enzyme, both in vitro and in vivo, was precipitated by antibody specific for the enzyme. Furthermore, the 32Pi counts were coincident with the enzyme subunit band when the immunoprecipitates were examined by sodium dodecyl sulfate/disc gel electrophoresis. Acid hydrolysis of the immunoprecipitated enzyme that was phosphorylated in vitro revealed that only seryl residues were labeled. On the basis of the concentration of protein kinase (0.2-1.0 muM) necessary to phosphorylate physiological amounts of fructose-1,6-bisphosphatase (1.0-4.0 muM), it is suggested that cyclic AMP-dependent protein kinase may catalyze the phosphorylation of fructose-1,6-bisphosphatase in vivo.
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PMID:In vivo and in vitro phosphorylation of rat liver fructose-1,6-bisphosphatase. 20 Sep 22

1. Calcium transport into microsomal vesicles of respiratory (tracheal) smooth muscle was characterized. This calcium transport was ATP dependent and stimulated by the presence of the oxalate ion. The magnitude of transport was similar to that reported for microsomes from other types of smooth muscle. 2. Bovine and rabbit, heavy and light microsomes were isolated from respiratory (tracheal) and vascular (aortic) smooth muscle. Preincubation of these vesicles with cyclic AMP and protein kinase did not alter the transport of calcium into the vesicles. There uas no evidence of phosphate incorporation into microsomal membrane proteins. Similar results were obtained if phosphorylase b kinase replaced the combination of cyclic AMP and protein kinase during the preincubation. 3. The phosphoprotein phosphatase activity of cardiac sarcoplasmic reticulum and smooth muscle microsomes was determined. The activity of this enzyme was found to be several-fold less in the cardiac sarcoplasmic reticulum than in various smooth muscle microsome preparations.
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PMID:Determination of calcium transport and phosphoprotein phosphatase activity in microsomes from respiratory and vascular smooth muscle. 20 Dec 93

Homogeneous cGMP-dependent protein kinase catalyzes the rapid incorporation of phosphate, specifically into the inhibitory subunit of purified cardiac troponin with a maximal incorporation of 1 mol of phosphate/mol of troponin. When troponin was incubated in the presence of both cGMP- and cAMP-dependent protein kinases, a maximal incorporation of 1 mol of phosphate/mol of troponin was observed which suggested phosphorylation of the same site by the two kinases. Both cyclic nucleotide-dependent kinases had similar Km values for troponin, but the Vmax value for the phosphorylation reaction catalyzed by cAMP-dependent protein kinase was 12-fold greater than the value obtained for cGMP-dependent protein kinase.
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PMID:Phosphorylation of cardiac troponin by guanosine 3':5'-monophosphate-dependent protein kinase. 20 26

Cyclic AMP- and cGMP-dependent protein kinases catalyze the phosphorylation of cardiac troponin inhibitory subunit (TN-I). Unlike many substrates utilized by both kinases, TN-I is rapidly phosphorylated using relatively low concentrations of the cGMP-dependent protein kinase (0.01 to 0.1 micrometer). At low concentrations of cAMP- and cGMP-dependent protein kinases, approximately twice as much total phosphate is incorporated into TN-I using the cAMP-dependent enzyme. At higher enzyme concentrations, 1 mol of phosphate/mol of TN-I is found using either enzyme. Maximal levels of cAMP- and CGMP-dependent protein kinases do not catalyze additive phosphorylation, suggesting that the two enzymes catalyze the phosphorylation of the same site on TN-I. The results support the concept of overlapping substrate specificity for cAMP- and cGMP-dependent protein kinases, but suggest that cardiac troponin contains additional specificity determinants for the cGMP-dependent protein kinase not found in several other protein substrates.
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PMID:Purified cyclic GMP-dependent protein kinase catalyzes the phosphorylation of cardiac troponin inhibitory subunit (TN-1). 20 27

The heat-stable protein (protein kinase modulator), partially purified from fresh bovine heart, possessed the ability to inhibit and stimulate adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase and guanosine 3':5'-monophosphate (cGMP)-dependent protein kinase activities, respectively. The inhibitory activity of protein kinase modulator on cAMP-dependent protein kinase was abolished almost completely by trypsin treatment, while the ability to stimulate cGMP-dependent protein kinase activity was resistant to trypsin. Fractionation by a linear potassium phosphate gradient on DEAE-cellulose column did not clearly separate both activities. Phosphorylation of cardiac microsomal component, "phospholamban" (molecular weight = 22,000), was inhibited almost completely by the saturating amounts of protein kinase modulator. This inhibition of phospholamban phosphorylation by protein kinase modulator was accompanied by a decreased Ca uptake rate that had been stimulated by cAMP-dependent protein kinase. These findings indicate that protein kinase modulator is functional in controlling the cAMP-dependent protein kinase-catalyzed phosphorylation of phospholamban and the rate of calcium transport, lending further support for the previously proposed mechanism, in which phospholamban is assumed to serve as a regulator of calcium transport in cardiac sarcoplasmic reticulum.
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PMID:Effect of protein kinase modulator on cAMP-dependent protein kinase-catalyzed phosphorylation of phospholamban and stimulation of calcium transport in cardiac sarcoplasmic reticulum. 20 86

1. Troponin I prepared from rabbit hearts contains 1.0-1.5 mol of P/mol when isolated by affinity chromatography. Most of the covalently bound phosphate is located in residues 1-48 of the molecule. 2. 3':5'-Cyclic AMP-dependent protein kinase catalyses phosphorylation at serine-20 and serine-146. Serine-20 is more rapidly phosphorylated than serine-146. 3. In troponin I prepared from frozen hearts by affinity chromatography about 0.3-0.5 mol of P/mol is associated with serine-20 and 0.8-1.0 mol of P/mol with other site(s) in residues 1-48 of the molecule. 4. Phosphorylation at serine-20 and servine-146 is not significantly inhibited by troponin C. 5. The mechansim of the interaction of troponin C with cardiac troponin I is discussed in the light of these results.
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PMID:The sites of phosphorylation of rabbit cardiac troponin I by adenosine 3':5'-cyclic monophosphate-dependent protein kinase. Effect of interaction with troponin C. 20 50


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