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 intracellular concentration of the 27-kDa mammalian heat shock protein, HSP27, increases several-fold after heat and other metabolic stresses and is closely associated with the acquisition of thermotolerance. Posttranslational modifications may also affect the function of HSP27. Heat shock of HeLa cell cultures, or treatment with arsenite, phorbol ester, or tumor necrosis factor, caused a rapid phosphorylation of preexisting HSP27 and the appearance of three phosphorylated isoforms, HSP27 B, C, and D. Digestion with trypsin and fractionation of the peptides by reverse phase high performance liquid chromatography revealed three 32P-labeled phosphopeptides. Microsequence analysis identified peak I as Ala76-Leu77-Ser78-Arg79 and peak II as Gln80-Leu81-Ser82-Ser83-Gly84-Val85- Ser86-Glu87-Ile88-Arg89; peak III contained the undigested peptide pair Ala76-Arg89. Ser82 was the major site and Ser78 the minor site of phosphorylation. Mutant proteins with Ser78 or Ser82 altered to glycine or Ser78-Ser82 double mutants were phosphorylated to reduced extents in vivo after heat or arsenite treatment. Ser78 and Ser82 (and Ser15) occur in the sequence motif RXXS, which is recognized by ribosomal protein S6 kinase II. Mitogenic stimulation of serum-deprived, Go-arrested Chinese hamster cells with serum, thrombin, or fibroblast growth factor also stimulated phosphorylation of HSP27 Ser78 and Ser82, and mitogenic stimulation and heat shock activated protein kinase activities that phosphorylated HSP27 and protein S6 in vitro. These results suggest that HSP27 may exert phosphorylation-activated functions linked with growth signaling pathways in unstressed cells. A homeostatic function at this level could protect cells from adverse effects of signal transduction systems which may be activated inappropriately during stress.
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PMID:Human HSP27 is phosphorylated at serines 78 and 82 by heat shock and mitogen-activated kinases that recognize the same amino acid motif as S6 kinase II. 173 Jun 70

Rabbit skeletal muscle membranes contain a protein which inhibits the cAMP-dependent protein kinase. The activity of the partially purified membrane protein is characterized by an IC-50 of 10 to 30 nM with respect to the inhibition of the activity of the catalytic subunit of the cAMP-dependent protein kinase and is sensitive to treatment with heat, acid, alkali and trypsin. The active fractions contain proteins ranging from 40 to 120 kDa, analysed by SDS-gel electrophoresis.
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PMID:Characterization and partial purification of a membrane protein from rabbit skeletal muscle which inhibits the cAMP-dependent protein kinase. 173 83

A protein kinase that is activated by calcium and lipid has been partially purified from the plasma membrane of oat roots. This protein kinase cross-reacts with four monoclonal antibodies directed against a soluble calcium-dependent protein kinase from soybean described previously [Putman-Evans, C. L., Harmon, A. C., & Cormier, M. J. (1990) Biochemistry 29, 2488-2495; Harper, J. F., Sussman, M. R., Schaller, G. E., Putnam-Evans, C., Charbonneau, H., & Harmon, A. C. (1991) Science 252, 951-954], indicating that the oat enzyme is a member of this calcium-dependent protein kinase family. Immunoblots demonstrate that the membrane-derived protein kinase is slightly larger than that observed in the cytosolic fraction of oat. Limited digestion of the membrane-derived kinase with trypsin generates a smaller water-soluble kinase that is still activated by calcium but is no longer activated by lipid. When posthomogenization proteolysis is minimized, the bulk of the immunoreactive kinase material is localized in the membrane. These results suggest that a calcium-dependent protein kinase observed in the supernatant fraction of oat extracts may originate in situ from a calcium- and lipid-dependent protein kinase which is associated with the oat plasma membrane. They further indicate that, in contrast to animal cells, the predominant calcium- and lipid-dependent protein kinase associated with the plasma membrane of plant cells has biochemical properties and amino acid sequence unlike protein kinase C.
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PMID:Characterization of a calcium- and lipid-dependent protein kinase associated with the plasma membrane of oat. 173 26

p19 is a highly conserved 19-kDa cytosolic protein that undergoes phosphorylation in mammalian cells upon activation of several distinct signal transduction pathways. Its expression is widespread but developmentally regulated. To determine the in vivo phosphorylation site(s) of p19, the protein was purified from bovine brain and resolved into the unphosphorylated form (p19) and a mixture of the two predominant phospho-forms (pp19). Proteolytic fragments of p19 and pp19 were examined by liquid chromatography/mass spectrometry (LC/MS). We detected ion masses corresponding to fragments spanning the entire amino acid sequence as deduced from the cDNA except for those predicted to contain an unmodified amino terminus. Instead, the digests revealed ions corresponding to peptides lacking the initiator methionine and containing an N-acetylated alanine at the amino terminus. The analysis of pp19, but not that of p19, revealed two sets of ions representing peptides whose m/z values differed by 80 atomic mass units, the incremental mass of a phosphate residue. These putative phosphate-bearing peptides were sensitive to alkaline phosphatase treatment. Using combined trypsin and V8 protease digestions, the phosphorylation sites were mapped to Ser-25 and Ser-38, in the peptides Leu-Ile-Leu-Ser*-Pro-Arg and Phe-Pro-Leu-Ser*-Pro-Pro-Lys, respectively. Interestingly, both phosphoserines are in a very similar sequence context, suggesting that a single proline-directed serine protein kinase, possibly p34cdc2, is responsible for phosphorylation of both sites in vivo.
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PMID:Analysis of phosphoprotein p19 by liquid chromatography/mass spectrometry. Identification of two proline-directed serine phosphorylation sites and a blocked amino terminus. 173 1

Externally oriented protein kinases are present on the plasma membrane of the human parasite, Leishmania. Since activation of complement plays an important role in the survival of these parasites, we examined the ability of protein kinases from Leishmania major to phosphorylate components of the human complement system. The leishmanial protein kinase-1 (LPK-1) isolated from promastigotes of L. major was able to phosphorylate purified human C3, C5 and C9. Only the alpha-chain of C3 and C5 was phosphorylated. The beta-chain appeared not to be a substrate for this enzyme. C3b which is formed by proteolytic cleavage of C3 was not phosphorylated by LPK-1. Trypsin treatment of phosphorylated C3 (P-C3) resulted in the disappearance of 32P from the alpha-chain. This was correlated with the conversion of the C3 alpha-chain to the alpha'-chain of C3b, and the appearance of a 9 kDa 32P fragment comigrating with the C3a fragment of C3. P-C3 was more resistant to cleavage by trypsin than nonphosphorylated C3. LPK-1 phosphorylated purified C3a and two synthetic peptides, C3a21R and YA-C3a10R, derived from its COOH-terminal end, which contain the C3a binding site to leukocytes and platelets. LPK-1 did not phosphorylate C3a8R. Phosphoamino acid analysis of the synthetic peptides indicated that serine 71 of C3a was phosphorylated by LPK-1. Treatment of C3 with either methylamine or freeze-thaw C3 (H2O) prevented phosphorylation by the LPK-1 suggesting that substrate conformation may be involved in recognition by the leishmanial enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Leishmanial protein kinases phosphorylate components of the complement system. 175 17

Studies with subconfluent day 2 cultures of rat myoblasts revealed that a cell surface 112 kDa protein could be phosphorylated by extracellular ATP. Analysis of the phosphorylated 112 kDa protein suggested the involvement of a serine protein kinase. The following evidence indicated the cell surface location of this protein kinase: (i) extracellular ATP was unable to penetrate the cell membrane under our experimental conditions; (ii) the phosphorylated protein profile of intact cells differed significantly from that of broken cells; (iii) the phosphorylation of the 112 kDa protein could be abolished by pretreatment of cells with very low concentrations of trypsin; (iv) the phosphorylated 112 kDa protein could be dephosphorylated by exogenously added alkaline phosphatase; (v) the phosphorylation of the 112 kDa protein was inhibited by exogenously added proteins; and (vi) exogenously added proteins could be phosphorylated by intact cells under similar experimental conditions. The phosphorylated 112 kDa protein was detected only when the reaction was carried out in the presence of Ca2+, Mg2+, and F- ions. Kinetic analysis that revealed that the Km value of the ecto-protein kinase for ATP was 0.04 microM, and the Vmax. value for phosphorylation of the 112 kDa protein was 1.67 x 10(-4) pmol/min per 10(5) cells. Data presented in the accompanying paper [Chen & Lo (1991) Biochem. J. 279, 475-482] show that there was a constant and adequate supply of ATP on the cell surface of rat myoblasts for efficient functioning of this protein kinase, and that mutants defective in either the ecto-protein kinase or the 112 kDa protein were also impaired in myogenic differentiation. This and other biochemical studies suggest that the ecto-protein kinase and the 112 kDa protein might play important roles in myogenic differentiation.
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PMID:Phosphorylation of a cell surface 112 kDa protein by an ecto-protein kinase in rat L6 myoblasts. 183 77

Mitogen-activated protein kinase (MAP kinase) is a 42 kd serine/threonine protein kinase whose enzymatic activity requires phosphorylation of both tyrosyl and threonyl residues. As a step in elucidating the mechanism(s) for activation of this enzyme, we have determined the sites of regulatory phosphorylation. Following proteolytic digestion of 32P-labeled pp42/MAP kinase with trypsin, only a single phosphopeptide was detected by two-dimensional peptide mapping, and this peptide contained both phosphotyrosine and phosphothreonine. The amino acid sequence of the peptide, including the phosphorylation sites, was determined using a combination of Fourier transform mass spectrometry and collision-activated dissociation tandem mass spectrometry with electrospray ionization. The sequence for the pp42/MAP kinase tryptic phosphopeptide is similar (but not identical) to a sequence present in the ERK1- and KSS1-encoded kinases. The two phosphorylation sites are separated by only a single residue. The regulation of activity by dual phosphorylations at closely spaced threonyl and tyrosyl residues has a functional correlate in p34cdc2, and may be characteristic of a family of protein kinases regulating cell cycle transitions.
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PMID:Identification of the regulatory phosphorylation sites in pp42/mitogen-activated protein kinase (MAP kinase). 184 75

Rap 1B is a low molecular weight G protein which is phosphorylated by cAMP-dependent protein kinase. In order to identify the site of phosphorylation by cAMP-dependent protein kinase, purified rap 1B from human platelets was phosphorylated and subjected to limited proteolysis with trypsin. Single digestion fragment containing the phosphorylation site was obtained and purified by reversed-phase HPLC. Sequence analysis of the phosphorylated digestion fragment demonstrated that the sequence of the phosphorylation site was -Lys-Lys-Ser-Ser-. This sequence is near the carboxy terminus and is adjacent to the site of membrane attachment of the protein.
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PMID:The localization of the cAMP-dependent protein kinase phosphorylation site in the platelet rat protein, rap 1B. 190 69

Proteolysis of the smooth muscle myosin-light-chain kinase with either thermolysin or endoproteinase Lys-C cleaves the enzyme towards the amino-terminus between the first and second unc domains, unc-II-1 and unc-II-2, and in the calmodulin-binding domain. The thermolytic fragment extends 532 residues from Ser275 to Ala806 and is resistant to further digestion. It is catalytically inactive and does not bind calmodulin. Further proteolysis of the thermolytic fragment with trypsin generates a constitutively active fragment. Digestion with endoproteinase Lys-C initially results in an inactive fragment of 516 residues, Ala287 to Lys802. Further digestion with Lys-C endoproteinase results in a constitutively active 474-residue fragment with the same amino-terminus, but a carboxyl-terminus at Lys760, near Arg762, the last conserved residue of protein kinase catalytic domains. There is no cleavage in the acidic-residue-rich connecting peptide between the amino-terminus of the catalytic domain and the unc-I domain, nor within the unc-II or unc-I domains or between the adjacent unc-II-2 and unc-I domains. The pattern of cleavages by these proteases reflects well the predicted domain structure of the myosin-light-chain kinase and further delineates the regulatory pseudosubstrate region. A synthetic peptide corresponding to the pseudosubstrate sequence, MLCK(787-807) was a more potent inhibitor by three orders of magnitude than the overlapping peptide MLCK(777-793) proposed by Ikebe et al. (1989) [Ikebe, M., Maruta, S. & Reardon, S. (1989) J. Biol. Chem. 264, 6967-6971] to be important in autoregulation of the myosin-light-chain kinase.
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PMID:Proteolytic cleavage sites in smooth muscle myosin-light-chain kinase and their relation to structural and regulatory domains. 191 44

The surface glycoproteins of influenza A viruses are the viral components first recognized by the immune system of the infected host, and they are the viral proteins first to contact the infecting cell. Cleavage of the hemagglutinin (HA) is the presupposition for the uptake and fusion between viral and endosomal membranes at a relatively low pH. If this cleavage does not occur during synthesis and migration within the cell, an external trypsin-like protease has to activate the virus with a non-cleaved HA. This latter property is presumably the reason, why such a large reservoir of non-pathogenic influenza A viruses could be built up in water fowl. Especially feral ducks can disseminate influenza viruses along their flight routes all over the world. The role of the neuraminidase (NA) in the infectious process is not so clear. Its main task in the natural infection seems to be removal of mucoids at the site of entry and in this way to start the primary infection. The synthesis of the viral proteins is a highly regulated process. There is not only a transcriptional but also a translational control. The viral glycoproteins belong to the late proteins. Specifically their synthesis can be inhibited by compounds acting in completely different ways like a specific methylase inhibitor (3DA-Ado), a protein phosphokinase C inhibitor (H7), or a lipid solvent (DMSO). It remains to be determined whether the underlining mechanism is in all these cases the same, namely posttranscriptional modification of viral mRNA. All these viral components do not act separately but they cooperate in their functions and sometimes interfere with each other.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Synthesis and function of influenza A virus glycoproteins. 193 Jan 3


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