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)

We are characterizing toxicant-induced injury to the nervous system by measuring nervous system, cell-type specific proteins together with accompanying changes in morphology and behavior. In the present study, cerebellar neurotoxicity was assessed in the Gunn rat, an autosomal recessive mutant that exhibits degeneration of Purkinje cells due to hereditary hyperbilirubinemia. Five proteins associated with neuronal or glial cell types were chosen for evaluation as follows: G-substrate, a Purkinje cell-specific phosphoprotein that serves as the endogenous substrate of cyclic GMP-dependent protein kinase; PCPP-260, a Purkinje cell-specific phosphoprotein that serves as an endogenous substrate of cyclic AMP-dependent protein kinase; synapsin I, a synapse-specific phosphoprotein present in all neurons; glial fibrillary acidic protein, an astrocyte-specific protein; and myelin basic protein, a protein unique to myelin. In comparison to heterozygote (Jj) controls, homozygous (jj) rats showed alterations in the amounts of neurotypic and gliotypic proteins in cerebellum that were consistent with the neuropathological effects associated with development of hyperbilirubinemia in the Gunn rat. Decreased cerebellar cyclic GMP, but not cyclic AMP, alterations in indices of motoric competence and increased responsiveness to a nociceptive stimulus also were observed in jj rats. In general, the degree of cerebellar hypoplasia was predictive of the degree of biochemical, morphological or behavioral change observed. The results indicate that neurotypic and gliotyic proteins may be used as biochemical indicators of neurotoxicity.
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PMID:Cerebellar hypoplasia in the Gunn rat is associated with quantitative changes in neurotypic and gliotypic proteins. 241 May 96

The substrate specificity of phospholipid/Ca2+-dependent protein kinase (protein kinase C) was studied using synthetic peptides, in particular those corresponding to the amino acid sequence around serine 115 in bovine myelin basic protein (MBP). It was found that MBP (104-118) and MBP (104-123) were substrates for the enzyme, with apparent Km values of 14 and 10 microM, respectively. Neither MBP (111-118) nor MBP (111-123) were phosphorylated, indicating that an additional segment of sequence extending toward the N terminus, but not toward the C terminus, was essential for the substrate activity of the peptides. Of the alanine-substituted analogs examined, [Ala 105] MBP (104-118) was comparable to the parent peptide, whereas [Ala 107] MBP (104-118) and [Ala 113] MBP-(104-118) were much poorer substrates. These findings indicated that lysine 105 was not essential, but both arginine 107 and arginine 113 were important specificity determinants. Initial studies revealed that [Ala 113] MBP (104-118) inhibited phosphorylation by the enzyme of the parent peptide and, to a lesser extent, the intact MBP(1-170). Serine 115 was the only site phosphorylated in the analog peptides [Ala 105] MBP (104-118) and [Ala 107]MBP (104-118). In the parent peptide, serine 115 was the initial site of phosphorylation but after prolonged phosphorylation other sites became phosphorylated (serine 110 and/or serine 112), further supporting the concept that arginine residues act as essential substrate specificity determinants for phospholipid/Ca2+-dependent protein kinase.
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PMID:Substrate specificity of phospholipid/Ca2+-dependent protein kinase as probed with synthetic peptide fragments of the bovine myelin basic protein. 241 12

The substrate specificity of protein kinase C was studied and compared with that of cyclic AMP-dependent protein kinase (protein kinase A) by using bovine brain myelin basic protein as a model substrate. This basic protein was phosphorylated at multiple sites by both of these protein kinases. In this analysis, the basic protein was thoroughly phosphorylated in vitro with [gamma-32P]ATP and each protein kinase, and then digested with trypsin. The resulting radioactive phosphopeptides were isolated by gel filtration followed by high performance liquid chromatography on a reverse-phase column. Subsequent amino acid analysis and/or sequential Edman degradation of the purified phosphopeptides, together with the known primary sequence of this protein, revealed that Ser-46 and Ser-151 were specifically phosphorylated by protein kinase C, whereas Thr-34 and Ser-115 were phosphorylated preferentially by protein kinase A. Both kinases reacted with Ser-8, Ser-11, Ser-55, Ser-110, Ser-132, and Ser-161 at various reaction velocities. Contrary to protein kinase A, protein kinase C appears to react preferentially with seryl residues that are located at the amino-terminal side close to lysine or arginine. The seryl residues that are phosphorylated commonly by these two protein kinases have basic amino acids at both the amino- and carboxyl-terminal sides. These results provide some clues to understanding the rationale that these kinases may show different but sometimes similar functions depending on the structure of target phosphate acceptor proteins.
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PMID:Studies on the phosphorylation of myelin basic protein by protein kinase C and adenosine 3':5'-monophosphate-dependent protein kinase. 241 24

The two most basic charge isomers of myelin basic protein (BP), components 1 and 2 (C1 and C2), which presumably differ in the degree of deamidation, were purified from bovine BP by cation-exchange chromatography. Two additional specific types of posttranslational modifications were introduced into the purified isomers: (1) C-terminal arginine deficient derivatives of C1 and C2 were prepared by incubating the isomers with a carboxypeptidase, and (2) phosphorylated derivatives of C1 (1.6 and 1.7 mol of phosphate/mol of protein) were prepared by incubating C1 with the protein kinase from rabbit muscle. The ability of these charge isomers to increase the permeability of multilamellar vesicles composed of phosphatidylserine/phosphatidylcholine (1:11.5 w/w) and sphingomyelin/cholesterol/phosphatidic acid (1:1:0.2 w/w/w) was measured by monitoring the release of a water-soluble spin-label (tempocholine chloride) from the vesicles. The increase in vesicle permeability caused by BP was taken as a measure of the degree of perturbation of the bilayer by the protein, most likely by penetration partly into the bilayer. All classes of charge isomers (naturally occurring or generated in vitro) were more effective at increasing vesicle permeability than was poly(L-lysine), a polycation that only interacts electrostatically with the bilayer. Although C1 and C2 and their C-terminal-deficient derivatives did not differ in the amount of marker released, the phosphorylated derivative of C1 caused a smaller increase in vesicle permeability than did the other isomers, suggesting that phosphorylation had altered the ability of the protein to perturb the bilayer.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Increase in vesicle permeability mediated by myelin basic protein: effect of phosphorylation of basic protein. 241 40

Synthetic peptide analogs of the bovine myelin basic protein (MBP) corresponding to residues 104-118 were found to specifically inhibit phospholipid/ Ca2+-dependent protein kinase (protein kinase C). The peptides [Ala107]MBP (104-118) and [Ala113]MBP (104-118) inhibited protein phosphorylation of intact MBP, histone H1 and peptide phosphorylation with MBP(104-123), MBP(104-118) or [Ala105]MBP (104-118) as substrates. The inhibitor peptides [Ala107]MBP(104-118) and [Ala113]MBP (104-118), containing alanine in place of the arginine recognition sites, apparently inhibited the enzyme noncompetitively with respect to substrates, with IC50 values ranging from 46-145 and 28-62 microM, respectively. These peptide analogs did not inhibit cyclic AMP-dependent protein kinase or myosin light chain kinase but inhibited phospholipid/Ca2+-dependent phosphorylation of endogenous proteins in the total, solubilized fraction of rat brain.
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PMID:Synthetic myelin basic protein peptide analogs are specific inhibitors of phospholipid/calcium-dependent protein kinase (protein kinase C). 241 28

In an effort to gain a more complete understanding of the regulation of myelin basic protein phosphorylation, we have been interested in defining further the mode of regulation of the myelin protein kinase involved in this posttranslational modification. Here we report the partial purification of a protein kinase from rat brain myelin. By gel filtration, it was determined that the molecular weight of this enzyme was in the range of 70-80 X 10(3) daltons Furthermore, it was established that at low calcium concentrations, this enzyme was markedly activated by phosphatidylserine in combination with either 4 beta-phorbol 12-myristate 13-acetate or diolein. The enzyme was not affected by cyclic AMP or by calcium, alone or in combination with calmodulin. On the basis of these findings this enzyme can be identified as a protein kinase C-like enzyme.
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PMID:Activation of myelin protein kinase by diacylglycerol and 4 beta-phorbol 12-myristate 13-acetate. 242 Sep 38

The peptide portion of the lipopeptide isolated from bovine myelin basic protein contained glycine, lysine, and serine in a 2:1:1 molar ratio as determined by amino acid analysis. The N-terminus of the peptide was determined to be glycine. The tetrapeptide Gly53-Ser-Gly-Lys56 was the only segment of myelin basic protein that matched the above two characteristics. This tetrapeptide is highly conserved among the myelin basic proteins sequenced so far. After the selective degradation of the lipopeptide, phosphoserine was identified in the acid hydrolysate, thus indicating that Ser-54 of myelin basic protein in bovine brain is the site of attachment of polyphosphoinositide. Interestingly, serine-54 of myelin basic protein can be phosphorylated by the endogenous protein kinase myelin. However, myelin basic protein phosphorylated by the catalytic subunit of an exogenous soluble protein kinase failed to produce radioactively labeled lipopeptide. Hence the endogenous enzymes of myelin are thought to be involved in the formation of the covalent linkage between polyphosphoinositide and myelin basic protein. The conservation in sequence suggests a possible important structural role for the "phospholipidation" of myelin basic protein.
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PMID:Covalent linkage of phospholipid to myelin basic protein: identification of serine-54 as the site of attachment. 242

Gangliosides have profound effects on the phosphorylation of several proteins in myelin. Addition of polysialogangliosides to purified guinea pig brain myelin enhanced the endogenous phosphorylation of a 62-kDa phosphoprotein, but completely inhibited the phosphorylation of myelin basic protein (MBP) (18.5 kDa). The ganglioside-stimulated phosphorylation of the 62-kDa protein was dose-dependent and -specific. Asialo-GM1, ceramide trihexosides, N-acetylneuraminic acid, or colominic acid alone could not mimic this effect, suggesting that the activation process requires both the hydrophobic head group and the anionic character of the gangliosides. Studies on the time course of this reaction revealed that it was a rapid and reversible process and was affected only very slightly by Ca2+. Thus, the stimulatory effect of gangliosides may not involve Ca2+-gangliosides complexes or proteolysis, but may be mediated through an activation of a ganglioside-dependent protein kinase or due to substrate protein-glycolipid interaction. Modulation of the phosphorylation of MBP by gangliosides varies with the states of phosphorylation of this protein. Prior addition of ganglioside to myelin inhibited the phosphorylation of MBP. However, addition of gangliosides to myelin subsequent to maximal phosphorylation of MBP retarded the dephosphorylation of this protein. Phosphorylation of isolated MBP by protein kinase C was stimulated by gangliosides, provided phosphatidylserine was present. In contrast, the glycolipid inhibited the phosphorylation of a unique site catalyzed by cAMP-dependent protein kinase. This site was distinct from those phosphorylated by protein kinase C and was also sensitive to chymotryptic cleavage. Although the exact physiological significance of protein phosphorylation in myelin has yet to be established, gangliosides may play an important role in the modulation of this reversible post-translational modification mechanism.
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PMID:Ganglioside-modulated protein phosphorylation in myelin. 243 83

Human myelin basic protein (MBP) was fragmented into three major polypeptides comprised of a NH2-terminal domain (residues 1-83), a middle domain (residues 84-119) which contains an experimental allergic encephalitogenic determinant and a highly conserved triproline sequence, and a COOH-terminal domain (residues 120-170) by Staphylococcus aureus V8 protease at pH 4.0. These three polypeptides could be identified and purified by reversed-phase high-performance liquid chromatography. Analysis of the sites of phosphorylation of the component 1 of human MBP, the most cationic species, catalyzed by a purified Ca2+-activated and phospholipid-dependent protein kinase and cAMP-dependent protein kinase revealed that although these protein kinases could incorporate approximately 6 and 4 mol 32P, respectively, into MBP, none of the potential sites were located within the middle domain.
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PMID:A novel fragmentation of human myelin basic protein: identification of phosphorylated domains. 243 24

A cyclic AMP and calcium-independent protein kinase has been identified and purified from pig brain to near homogeneity. This independent protein kinase was isolated in an inactive form, and activation required ATP and Mg2+. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the purified enzyme contains 1 subunit with a molecular mass of about 36 kDa. Although there was no significant phosphorylation of phosphorylase, phosphorylase b kinase, casein, phosvitin, and protamine, this kinase was found to be very active toward myelin basic protein and histones H1, 2A, and 2B. Trypsinolysis completely destroyed the kinase activity, indicating that this is not a protease-activated protein kinase. More interesting, this cAMP and calcium-independent protein kinase can be regulated by its state of phosphorylation. In its non-phosphorylated state, the kinase was essentially inactive but could be fully activated when the enzyme was phosphorylated up to a 1:1 molar ratio. Conversely, partial dephosphorylation of the phosphorylated enzyme was associated with a time-dependent decrease in the kinase activity and a loss of 32P. All the results taken together point out that this kinase is distinguished from all the reported protein kinases and may represent a previously undiscovered protein kinase. The results also provide initial evidence that a cascade activation mechanism may possibly be involved in the regulation of a protein kinase activity which is independent of cAMP and calcium.
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PMID:Identification and characterization of a phosphorylation-activated, cyclic AMP and Ca2+-independent protein kinase in the brain. 243 73


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