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)

A protein kinase specific for casein and acidic ribosomal proteins was isolated and partly characterized. It was found that the enzyme utilizes GTP and ATP as phosphoryl donors. Its affinity for ATP was considerably higher than for GTP with the km values of 7.6 X 10(-6)M and 5.5 X 10(-5)M, respectively. Two-dimensional acrylamide gel electrophoresis revealed the phosphorylation of the same ribosomal proteins with either of the [gamma-32P] nucleotides used. It was also shown that one acidic protein (S1 or S2) of 40 S and two acidic proteins (L2 and L3) of 60 S ribosomal subunits were predominantly phosphorylated in vitro. The phosphorylated proteins: L2 and L3 seem to correspond to the proteins of L7 and L12 of E. coli ribosomes. The isolated kinase phosphorylated several basic ribosomal proteins though to a lower extent than the acidic ones.
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PMID:Ribosomal protein as substrate for a GTP-dependent protein kinase from yeast. 79 85

A translational inhibitor has been isolated from unstimulated Friend leukemia cells. The inhibitor is a heat-labile, sulfhydryl reagent-insensitive protein with a molecular weight of approximately 214,000. It inhibits protein synthesis at a step of peptide chain initiation by preventing initiation factor-dependent binding of methionyl-tRNAf to 40 S ribosomal subunits. However, it does not interfere with the formation of the ribosome-independent ternary complex between the initiation factor IF-E2, methionyl-tRNAf, and GTP. The inhibitor preparation contains protein kinase activity which phosphorylates the smallest subunit of IF-E2. There appears to be a functional similarity between this inhibitor from Friend leukemia cells and the hemin-controlled repressor from reticulocytes.
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PMID:Partial purification and characterization of a translational inhibitor from Friend leukemia cells. 84 64

Two acidic proteins from 80-S ribosomes were isolated and purified to homogeneity. The purified acidic proteins could be phosphorylated by casein kinase using [gamma-32P]ATP and [gamma-32P]GTP as a phosphoryl donor. The proteins became phosphorylated in situ, too. Sodium dodecyl sulfate polyacrylamide gel analysis of the purified acidic proteins and 80-S particles showed identical phosphoproteins in the 16 000 dalton region.
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PMID:Phosphorylation of acidic ribosomal proteins from rabbit reticulocytes by a ribosome-associated casein kinase. 88 11

A casein kinase was isolated and purifed from rabbit reticulocytes. About 90% of the enzyme activity co-sedimented with the ribosomal fraction, whereas about 10% of the enzyme activity was found in the ribosome-free supernatant. Both casein kinases (the ribosome-bound enzyme as well as the free enzyme) showed identical activity and the same molecular weight. On sodium dodecyl sulphate/polyacrylamide-gel electrophoresis a single band of about 70 000 mol.wt. was observed. Sucrose-gradient analysis, however, showed that the enzyme activity sedimented with a s20,w of approx. 7.5S. This observation suggested that the casein kinase is a dimer composed of subunits of identical molecular weight. The enzyme utilizes GTP as well as ATP as a phosphoryl donor. It preferentially phosphorylates acidic proteins, in particular the model substrates casein and phosvitin. Casein kinase is cyclic AMP-indepenoent. The Km values for ATP and GTP with phosvitin as a substrate were determined as 1.2 and 8.8 micrometer respectively.
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PMID:Purification and properties of a ribosomal casein kinase from rabbit reticulocytes. 92 64

Initiation factor IF-E2 was isolated from rabbit reticulocytes and purified 120-fold to near homogeneity by ammonium sulfate fractionation, column chromatography on DEAE-cellulose and phosphocellulose, and, when suitable, by sucrose density gradient centrifugation. The factor is a complex protein containing three nonidentical polypeptides of molecular weight 57,000, 52,000, and 36,000. It behaves as a complex throughout its purification and during polyacrylamide gel electrophoresis in nondenaturing buffer but its thress components are readily separated by electrophoresis in denaturing buffers. None of its components corresponds to any of the polypeptides of the other initiation factors or to any proteins of ribosomes washed in buffers containing a high salf concentration. A stoichiometric ratio of 1:1:1 was determined for the three polypeptides; based on the assumption of one copy each per complex, the calculated factor molecular weight is 145,000, a value in agreement with the measured value of 160,000. Initiation factor IF-E2 was radioactively labeled in vitro by reductive alkylation or by phosphorylation with a protein kinase also isolated from rabbit reticulocytes. Neither procedure causes a measurable change in the ability of the factor to form a ternary complex with GTP and the initiator methionyl-tRNA. 5'-Guanylyl-methylenediphosphonate may substitute for GTP, but only at relatively high concentrations. The binding of labeled initiation factor IF-E2 and methionyl-tRNA to the 40 S ribosomal subunit was studied by sucrose density gradient centrifugation. Appreciable binding of the factor is seen only when all three components of the ternary complex are included in the reaction mixture. The binding of either the factor or methionyl-tRNA was not stimulated by the addition of globin messenger RNA and initiation factor IF-E3. It was shown that all three polypeptide components of initiation factor IF-E2 are bound to these nascent initiation complexes.
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PMID:Purification and characterization of initiation factor IF-E2 from rabbit reticulocytes. 100 8

The heme-regulated translational inhibitor (HRI) has been purified 4800-fold. On electrophoresis in sodium dodecyl sulfate/polyacrylamide gel, the purified HRI showed one major polypeptide band. The purified HRI inhibits protein synthesis in lysates containing optimal levels of hemin with inhibition kinetics which parallel those observed in heme-deficiency. Data are presented which are consistent with an enzymatic function of HRI in the inhibition of protein synthesis. The HRI is an adenosine 3':5'-cyclic monophosphate independent protein kinase which phosphorylates the small subunit (38,000) but not the large subunits (52,000 and 50,000) of the initiation factor which forms a ternary complex with Met-tRNAf and GTP. This evidence supports the hypothesis that inhibition of protein synthesis by HRI involves the phosphorylation of the initiation factor. These findings are discussed in relation to various models for the regulation of protein kinase activity by heme. (see article).
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PMID:Regulation of protein synthesis in rabbit reticulocyte lysates: purification and initial characterization of the cyclic 3':5'-AMP independent protein kinase of the heme-regulated translational inhibitor. 106 87

Two protein kinases differing in substrate specificity were used to phosphorylate the 30-S and the 50-S ribosomal subunits of Escherichia coli. The catalytic subunit from the rabbit skeletal muscle protein kinase phosphorylates proteins S1, S4, S9, S13 and S18 of the 30-S subunit and proteins L2, L4, L5, L16, L18 and L23 of the 50-S subunit with (gamma-32P)ATP as phosphoryl donor. A second protein kinase isolated from rabbit reticulocytes, formerly shown to phosphorylate preferentially acidic proteins and to use GTP as well as ATP, strongly phosphorylated protein S6, an acidic protein of the small ribosomal subunit, and to a lesser extent proteins L7 and L12 or the large subunit. Evidence is presented showing different phosphorylation patterns when either whole subunits or the extracted proteins were used as substrate for the protein kinase. Kinetic studies showed proteins S1 and S4 to become most rapidly phosphorylated. Although most proteins incorporated less than stoichiometric amounts of phosphate, it is shown that with a high excess of ATP L2 bound 1 mol phosphate/mol protein.
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PMID:Specificity of ATP-dependent and GTP-dependent protein kinases with respect to ribosomal proteins of Escherichia coli. 110 23

The regulation of Cl- channels in human myoballs by G proteins was studied using whole-cell and inside-out patch recordings. After perfusion of the cell with 0.1 mM GTP[gamma S], the specific Cl- conductance, GCl, at standard resting potential (-85 mV) was increased from 5.9 microS/cm2 to 103 microS/cm2, and the kinetics upon stepping the potential to positive values was changed from an activating current with very slow inactivation to a fast inactivating current with no potential-dependent activation. These effects were not affected by the simultaneous blockade of several signal cascades involving G proteins. Addition of the protein kinase blockers PKI (25 microM), H8 (10 microM), or of the phospholipase-A2-blocking agent quinacrine (10 microM), had not much influence on these GTP[gamma S] effects. Buffering of the intracellular Ca2+ concentration (0.1 microM) or addition of the Ca2+/calmodulin antagonist trifluoperazine (50 microM) was also without effect. Pre-incubation of the cells with pertussis toxin or with cholera toxin did not change GCl. In excised inside-out patches voltage-clamped at -85 mV, application of GTP[gamma S] influenced the "intermediate" Cl- channel, the Cl- channel type having the highest density in these cells, by increasing the number of transitions in a half-conductance state. The probability of the channel being in one of the two conducting states rose from 0.015 to 0.67, and the kinetics of the single-channel currents was changed so that, on average, it was similar to the whole-cell current kinetics seen after application of GTP[gamma S]. It is concluded that a G protein is directly interacting with these channels.
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PMID:Chloride channels in cultured human skeletal muscle are regulated by G proteins. 127 15

Prenalterol, an allegedly beta 1-selective adrenergic agonist with high intrinsic sympathomimetic activity (ISA), was shown to be weakly lipolytic in rat adipocytes. However, in pertussis-toxin-treated adipocytes, the ISA of prenalterol was markedly increased (from 10-20% to approx. 100% of that of isoprenaline). The cellular sensitivity was also increased (EC50 approx. 60 nM and approx. 3 microM in pertussis-toxin-treated and control cells respectively). A similar effect was seen for other partial agonists such as the beta 2-selective agonist terbutaline and for beta-adrenergic antagonists with some intrinsic activity (metoprolol, pindolol). There was no clear change in sensitivity to isoprenaline's ability to stimulate adenylate cyclase in adipocyte membranes from pertussis-toxin-treated animals but the cyclase activity was increased approx. 4-fold in the presence of 1 microM-GTP. Prenalterol stimulated lipolysis by only small increases in intracellular cyclic AMP (cAMP) levels (less than 10% of that seen with isoprenaline). Basal lipolysis was increased in cells from pertussis-toxin-treated rats and the cellular sensitivity to the non-degradable cAMP analogue, N6-monobutyryl-cAMP, was increased. In control cells, a submaximal concentration of prenalterol (0.1 microM) increased the sensitivity to the cAMP analogues, N6-monobutyryl-cAMP and 8-bromo-cAMP. A low concentration (1 mM) of 8-bromo-cAMP also increased the effect of prenalterol. Similar effects were seen when the phosphodiesterase was inhibited. Thus (1) lipolysis is extremely sensitive to small increases in intracellular cAMP; (2) the degree of activation of adenylate cyclase and thus cAMP formation is the rate-limiting step for the biological response of partial agonists; (3) the inhibitory GTP-binding protein, Gi, is an important modulator ('tissue factor') of the beta-adrenergic agonistic property; (4) low levels of cAMP exert a priming effect on protein kinase A.
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PMID:The inhibitory GTP-binding protein (Gi) regulates the agonistic property of beta-adrenergic ligands in isolated rat adipocytes. Evidence for a priming effect of cyclic AMP. 128 Jan 15

Two protein kinases active on casein and phosvitin were partially purified from the soluble fraction of ejaculated bovine spermatozoa. They were operationally termed casein kinase A and B based on the order of their elution from a phosphocellulose column. CK-A showed an approximate molecular mass of 38 kDa, and it phosphorylated serine residues of casein and phosvitin utilizing ATP as a phosphate donor (Km 19 microM). Enzyme activity was maximal in the presence of 10 mM MgCl2, whereas it decreased in the presence of spermine, polylysine, quercetin, and NaCl (20-250 mM). CK-B seemed to have a monomeric structure of about 41 kDa; it underwent autophosphorylation and cross-reacted with polyclonal antibodies raised against recombinant alpha, but not beta, subunit of human type 2 casein kinase. It phosphorylated both serine and threonine residues of casein and phosvitin, utilizing ATP (Km 12 microM) but not GTP as a phosphate donor. Threonine was more affected in the phosphorylated phosvitin than in the partially dephosphorylated substrate. CK-B was active toward the synthetic peptide Ser-(Glu)5 and calmodulin (in the latter case, in the presence of polylysine), and it was activated by spermine, polylysine, MgCl2 (30 mM), and NaCl (20-400 mM). The activity of the enzymes was not affected by cAMP, or the heat-stable inhibitor of the cAMP-dependent protein kinase, or calcium.
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PMID:Purification and characterization of two casein kinases from ejaculated bovine spermatozoa. 129 85


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