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)

Two series of synthetic peptides that reproduce the amino- and carboxyl-terminal segments of the beta-subunit of casein kinase-2, including the sites phosphorylated by CK2 and cdc2 kinase, respectively, have been used as model substrates for these enzymes. The N-terminal peptide beta(1-9), MSSSEEVSW, is readily phosphorylated by CK2 but not all by cdc2. The opposite is true of the C-terminal peptide beta(206-215), NFKSPVKTIR, whose Ser-4 is a good target for cdc2 while being unaffected by CK2. The individual substitutions of Pro-5 and Lys-7 in the latter peptide with Gly and Ala (or Glu), respectively, prevent its phosphorylation by cdc2, whereas the substitution of Lys-3 with Ala is well tolerated and the substitution of the target Ser with Thr actually improves phosphorylation. Thus the consensus sequence for cdc2 is shown to be X-S-P-X-K. Such a requirement for a basic residue at position +3 is opposite to that of CK2 whose consensus sequence (S-X-X-E/D/Yp/Sp) includes an acidic residue at the same position. Moreover the motif Ser-Pro is detrimental for CK2, preventing the phosphorylation of otherwise suitable peptides. These observations would rule out the possibility that the site specificity of CK2 might overlap with that of cdc2 and possibly of other Pro-directed protein kinases.
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PMID:The consensus sequences for cdc2 kinase and for casein kinase-2 are mutually incompatible. A study with peptides derived from the beta-subunit of casein kinase-2. 145 79

The catalytic subunit of cAMP-dependent protein kinase contains two stable phosphorylation sites, Thr-197 and Ser-338 (Shoji, S., Titani, K., Demaille, J. G., and Fischer, E. H. (1979) J. Biol. Chem. 254, 6211-6214). Thr-197 is very resistant to dephosphorylation and thus cannot typically be autophosphorylated in vitro once the stable subunit is formed. Ser-338 is slowly dephosphorylated and can be rephosphorylated autocatalytically. In addition to these two stable phosphorylation sites, a new site of autophosphorylation, Ser-10, was identified. Phosphorylation at Ser-10 does not have a major effect on activity, and phosphates from Ser-10 or Ser-338 are not transferred to physiological substrates such as the type II regulatory subunit. Autophosphorylation at Ser-10 is associated with one of the two major isoelectric variants of the catalytic subunit. The form having the more acidic pI can be autophosphorylated at Ser-10 while the more basic form of the catalytic subunit cannot. Phosphorylation at Ser-10 does not account for the two isoenzyme forms. Since the reason for two isoelectric variants of the catalytic subunit is still unknown, it is not possible to provide a structural basis for the difference in accessibility of Ser-10 to phosphorylation. Either Ser-10 is not accessible in the more basic form of the catalytic subunit or some other type of post- or cotranslational modification causes Ser-10 to be a poor substrate. Whether the myristoyl group at the amino-terminal Gly is important for Ser-10 autophosphorylation remains to be established. The isoenzyme forms of the catalytic subunit do not correspond to the gene products coded for by the C alpha and C beta genes.
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PMID:Autophosphorylation of the catalytic subunit of cAMP-dependent protein kinase. 146 17

Like many other cell surface receptors for nutrients and polypeptide hormones, the insulin receptor undergoes a complex endocytotic itinerary. Upon insulin binding, the receptor is activated as a tyrosine-specific protein kinase and autophosphorylates. This autophosphorylation is necessary for the receptor to internalize. After endocytosis, the ligand (insulin) and its receptor are dissociated. Most of the insulin is degraded, whereas the receptors are largely recycled to the cell surface. The signals in the receptor that control and specify its endocytotic pathway are beginning to be understood. Through the techniques of in vitro mutagenesis, noninternalizing receptors have been engineered and their structural and functional properties have been analyzed. For example, the immediate submembranous domain of the insulin receptor has been found to contain sequences (Gly-Pro-Leu-Tyr and, to a lesser extent, Asn-Pro-Gln-Tyr) that are necessary for normal endocytosis. Receptors deleted or mutated in these sequences retain tyrosine kinase activity but fail to undergo endocytosis. Unlike the better understood low density lipoprotein and transferrin receptors, however, these sequences are not sufficient for endocytosis. An insulin receptor with only these sequences exposed in the cytoplasm does not internalize. Tyrosine kinase activity is thought to be needed to lead to autophosphorylation and a conformational change that exposes the otherwise buried endocytosis sequences in the normally dimerized insulin receptor. Non-internalizing mutants of the insulin receptor have been used to examine the role of endocytosis in insulin action. It was found that an endocytosis-defective receptor could induce a short-term metabolic action of insulin (glycogen synthetase stimulation) as well as longer-term mitogenic effects of insulin. Furthermore, insulin action deactivated after the hormone was removed from the noninternalizing receptors. Apparently, endocytosis is not necessary for insulin action, but probably is important for removing the insulin from the cell so the target cell for insulin responds in a time-limited fashion to the hormone.
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PMID:Mechanism and role of insulin receptor endocytosis. 147 59

In regenerating rat liver, nuclear protein histone H2A was shown to be phosphorylated on its amino-terminal serine residue [Sung et al. (1971) J. Biol. Chem. 246, 1358-1364], but the protein kinase which phosphorylates this residue has not been identified. To evaluate the possibility that protein kinase C can phosphorylate this residue, calf thymus histone H2A was 32P-labeled by incubation with [gamma-32P]ATP and highly purified protein kinase C from rat brain in the presence of calcium and phospholipid. About 1 mol of 32P was incorporated per mol of histone H2A and the Km and apparent Vmax of the reaction were calculated to be 2.1 microM and 0.35 mumol/min/mg, respectively. So histone H2A seemed to be a good substrate for protein kinase C. Further, the proteolytic phosphopeptides of 32P-labeled histone H2A were isolated by means of a series of column chromatographies and analyzed for their amino acid compositions. Comparison of the data with the known primary structure of histone H2A revealed their amino acid sequence as 1Ser-Gly-Arg. These data suggest that protein kinase C may be a candidate for the protein kinase which phosphorylates the amino-terminal serine residue of histone H2A during the regeneration of rat liver.
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PMID:Phosphorylation of histone H2A by protein kinase C and identification of the phosphorylation site. 150 Apr 20

A cytosolic insulin-sensitive serine kinase has been purified to apparent homogeneity in parallel from livers of control or acutely insulin-treated rats. The kinase is labile and requires rapid purification for stability. The kinase migrates as a band of apparent Mr = 90,000 on denaturing gels and elutes as a monomer on Superose 12 gel filtration. After sodium dodecyl sulfate-polyacrylamide gel electrophoresis and renaturation, the 90-kDa band presumed to be the kinase shows kinase activity toward myelin basic protein in situ. Substrates of the kinase include Leu-Arg-Arg-Ala-Ser-Leu-Gly (Kemptide), ribosomal protein S6, S6 peptide, a proline-rich peptide substrate, microtubule-associated protein 2, and myelin basic protein. The kinase also phosphorylates histones H1 and H2B, but does not autophosphorylate to a significant stoichiometry. The activity of the kinase is inhibited by fluoride, glycerophosphate, p-nitrophenyl phosphate, p-nitrophenol, heparin, quercetin, poly-L-lysine, and potassium phosphate, but is unaffected by calcium, cAMP, spermine, protein kinase inhibitor peptide, phorbol myristate acetate, calcium plus phosphatidylserine, or vanadate. The kinase will utilize magnesium (10 mM) as well as manganese (1 mM) as a cofactor for maximal phosphotransferase activity. The kinase is not detected by immunoblotting with antibodies directed against protein kinase C or type II S6 kinase. Taken together, these properties distinguish this kinase from other insulin-sensitive kinases that have been described previously. The purified kinase from livers of insulin-treated rats shows a 5-20-fold higher specific activity compared to enzyme prepared from control rats, suggesting a covalent modification as the mechanism of activation. Incubation of purified, insulin-stimulated kinase with purified phosphatase 2A leads to deactivation of the kinase activity, and the phosphatase inhibitor nitrophenyl phosphate blocks this deactivation. The insulin-activated kinase fails to immunoblot with anti-tyrosine phosphate antibodies. Taken together, these results indicate that insulin activates this novel cytosolic protein kinase by a mechanism that causes its phosphorylation on serine or threonine residues.
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PMID:Purification and characterization of a cytosolic insulin-stimulated serine kinase from rat liver. 153 38

A library of mutants of the catalytic subunit of the Saccharomyces cerevisiae cAMP-dependent protein kinase was screened in vitro for mutants defective in the recognition of the regulatory subunit. The mutations identified were mapped onto the three-dimensional structure of the mouse catalytic subunit with a peptide inhibitor. Mutations defective in the recognition of both the regulatory subunit and the peptide substrate Leu-Arg-Arg-Ala-Ser-Leu-Gly (Kemptide) mapped to the peptide-binding site shared by all substrates and inhibitors of the catalytic subunit and functionally define the binding site for the autoinhibitor sequence in the hinge region of the regulatory subunit. Mutants defective only in the recognition of the regulatory subunit identified residues that comprise additional binding sites for the regulatory subunit. The majority of these residues are clustered on the surface of the catalytic subunit in a region flanking the distal portion of the autoinhibitor/peptide-binding site. The simultaneous substitution of Lys233, Asp237, Lys257, and Lys261 in this region caused a 260-fold decrease in affinity for the regulatory subunit, whereas the catalytic efficiency toward Kemptide decreased by only 1.8-fold. The substitution of autophosphorylated Thr241, also in this region, and the 3 residues interacting with the phosphate also caused an unregulated phenotype.
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PMID:Systematic mutational analysis of cAMP-dependent protein kinase identifies unregulated catalytic subunits and defines regions important for the recognition of the regulatory subunit. 153 60

In this paper, we demonstrate that synthetic epidermal mitosis inhibiting pentapeptide (pyroGlu-Glu-Asp-Ser-Gly) is phosphorylated in vitro at serine level by protein kinase NII isolated from calf thymus chromatin. A serum enzyme, which rapidly cleaves the synthetic epidermal mitosis inhibiting pentapeptide, also hydrolyses the synthetic transcription inhibiting pentapeptide (pyroGlu-Ala-Glu-Ser-Asn). The phosphorylated forms of both pentapeptides are protected from the serum enzyme activity.
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PMID:Epidermal inhibitory pentapeptide phosphorylated in vitro by calf thymus protein kinase NII is protected from serum enzyme hydrolysis. 155 May 57

We investigated the relationship of polymorphonuclear leukocyte (PMN) candicidal activity, matrix proteins, and lipopolysaccharide (LPS) to determine how LPS modulates the normal enhancing effect of matrix proteins on PMN candicidal activity. LPS reduced PMN candicidal activity when PMN were adhered in the presence of either fibronectin or laminin. In the presence of fibronectin or laminin, LPS reduced CD11b/CD18 expression (the fibronectin receptor) as assessed using sheep erythrocytes coated with C3bi. Experiments with 125I-fibronectin and 125I-RGDS (Arg-Gly-Asp-Ser) demonstrated that LPS reduced both the binding of fibronectin and the bioavailability of the binding epitope on the PMN surface. Stimulating the PMN oxidative burst with PMA but not FMLP also reduced fibronectin and RGDS binding. Incubation of LPS-treated PMN with staurosporine blocked the decrease in fibronectin and RGDS binding. Exposure of PMN to LPS plus low-dose TNF-alpha restored both fibronectin and RGDS binding with a concomitant increase in CD11b/CD18 surface expression. Low-dose TNF-alpha restored PMN candicidal activity in the presence of LPS and was most effective if PMN were preadhered to fibronectin. These results demonstrate that: (1) matrix proteins enhance normal PMN candicidal activity, (2) LPS reduces PMN candicidal activity in the presence of matrix proteins, (3) stimulation of the PMN oxidative burst in particular via protein kinase c activation reduces the bioavailability of the fibronectin receptor, and (4) low-dose TNF-alpha may restore PMN candicidal activity in part by upregulating the surface receptor for fibronectin binding.
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PMID:Endotoxin suppresses matrix protein-induced upregulation of PMN candicidal activity: an effect reversed by low-dose TNF-alpha. 161 18

Stimulation of PMN with inflammatory mediators markedly augments Fc and CR1 receptor-mediated ingestion. However, CD11/CD18-deficient PMN from three patients with complete leukocyte adhesion deficiency (LAD) failed to recruit phagocytic function in response to phorbol esters, cytokine, or Arg-Gly-Asp-containing ligand stimulation. Because stimulated ingestion is protein kinase C (PKC)-dependent, our data indicate that LAD PMN exhibit only PKC-independent phagocytosis. The defect in PKC-dependent ingestion is specific for CD11b/CD18 and not secondary to the chronic or recurrent infections which occur in this disease. The LAD phenotype for phagocytic function can be reproduced in normal PMN by the anti-CD11b MAbs OKM1 and OKM10. In contrast, MAb Mo1 (anti-CD11b) and MAb IB4 (anti-CD18) inhibit both CD11b/CD18-dependent and -independent mechanisms of ingestion by normal PMN. Their ability to inhibit CD11b/CD18-independent ingestion may be mediated by cAMP, as shown by experiments with a protein kinase A inhibitor HA1004 and by direct measurement of cAMP levels in immune complex- and FMLP-stimulated PMN. These data indicate that CD11b/CD18-independent and -dependent mechanisms of phagocytosis exist and that some effects of anti-CD11b/CD18 MAbs may be mediated by alterations in cAMP levels.
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PMID:Leukocyte adhesion-deficient neutrophils fail to amplify phagocytic function in response to stimulation. Evidence for CD11b/CD18-dependent and -independent mechanisms of phagocytosis. 167 46

1. In isolated rat adipocytes, acetyl-CoA carboxylase is inactivated by treatment of the cells with adrenaline or the beta-agonist isoproterenol, but not by the alpha-agonist phenylephrine. The inactivation is stable during purification in the presence of protein phosphatase inhibitors, and is associated with a 30-40% increase in the labelling of enzyme isolated from 32P-labelled cells. 2. Increased phosphorylation occurs within peptide T1, which was identified by sequencing to be the peptide Ser-Ser77-Met-Ser79-Gly-Leu-His-Leu-Val-Lys, containing Ser-77 (phosphorylated by cyclic-AMP-dependent protein kinase) and Ser-79 (phosphorylated by the AMP-activated protein kinase). Analysis of the release of radioactivity as free phosphate during Edman degradation of peptide T1 revealed that all of the phosphate was in Ser-79 in both basal and hormone- or agonist-stimulated cells. Treatment of adipocytes with various agents which activate cyclic-AMP-dependent protein kinase by receptor-independent mechanisms (forskolin, cyclic AMP analogues, isobutylmethylxanthine) also produced inactivation of acetyl-CoA carboxylase and increased phosphorylation at Ser-79. 3. The (Rp)-[thio]phosphate analogue of cyclic AMP, which is an antagonist of binding of cyclic AMP to the regulatory subunit of cyclic-AMP-dependent protein kinase, opposes the effect of adrenaline on phosphorylation and inactivation of acetyl-CoA carboxylase. Together with the effects of isobutylmethylxanthine and the stimulatory cyclic AMP analogues, this strongly indicates that cyclic-AMP-dependent protein kinase is an essential component of the signal transduction pathway, although clearly it does not directly phosphorylate acetyl-CoA carboxylase. 4. As shown by okadaic acid inhibition, greater than 95% of the acetyl-CoA carboxylase phosphatase activity in extracts of rat adipocytes or liver is accounted for by protein phosphatase-2A, with less than 5% attributable to protein phosphatase-1. Inhibition of protein phosphatase-1 via phosphorylation of inhibitor-1 is therefore unlikely to be the mechanism by which cyclic-AMP-dependent protein kinase indirectly increases phosphorylation of acetyl-CoA carboxylase. Various other potential mechanisms are discussed.
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PMID:Roles of the AMP-activated and cyclic-AMP-dependent protein kinases in the adrenaline-induced inactivation of acetyl-CoA carboxylase in rat adipocytes. 168 96


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