Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The hypothesis that casein kinase II (CKII) is a microtubule-associated protein kinase was investigated using a neuronal cell line and bovine brain. Heparin, an inhibitor of CKII, inhibited the phosphorylation of a PC12 cytosolic protein whose molecular weight was similar to that of beta-tubulin. Partially purified PC12 CKII was immunoreactive to an antibody directed against bovine CKII and was able to phosphorylate purified beta-tubulin in a heparin-inhibitable manner when the concentration of tubulin was less than 50 micrograms/ml. To better determine if CKII is a microtubule-associated protein kinase, bovine brain tubulin was chromatographed on FPLC Mono Q and phosphocellulose columns. Several tubulin casein kinase (TCK) activities were apparent. All TCK activities phosphorylated tubulin and casein, but none was able to phosphorylate the CKII-specific synthetic peptide RRREEETEEE. One of these TCK fractions was immunoreactive to the antibody directed against CKII, and this antibody labeled a 50-kDa molecular mass band that had a molecular mass distinctly different from those of the subunits of CKII. Thus, we suggest that a CKII-like protein, but not CKII, might be a microtubule-associated protein.
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PMID:A casein kinase-like kinase phosphorylates beta-tubulin and may be a microtubule-associated protein. 143 92

Casein kinase II (CKII) is one of several protein kinases that become activated before germinal-vesicle breakdown in maturing sea-star oocytes. Echinoderm CKII was purified over 11,000-fold with a recovery of approximately 10% by sequential fractionation of the oocyte cytosol on tyrosine-agarose, heparin-agarose, casein-agarose and MonoQ. The purified enzyme contained 45, 38 and 28 kDa polypeptides, which corresponded to its alpha, alpha' and beta subunits respectively. The beta-subunit was autophosphorylated on one major tryptic peptide on serine residues, whereas the alpha'-subunit incorporated phosphate into at least two tryptic peptides primarily on threonine residues. Western-blotting analysis of sea-star oocyte extracts with two different anti-peptide antibodies that recognized conserved regions of the alpha-subunit indicated that the protein levels of the alpha- and alpha'-subunits of CKII were unchanged during oocyte maturation. The purified CKII was partly inactivated (by 25%) by preincubation with protein-serine/threonine phosphatase 2A, but protein-tyrosine phosphatases had no effect. The beta-subunit of CKII was phosphorylated on a serine residue(s) up to 0.54 mol of P/mol of beta-subunit by purified protein kinase C, and this correlated with a 1.5-fold enhancement of its phosphotransferase activity with phosvitin as a substrate. CKII was not a substrate for the maturation-activated myelin basic protein kinase p44mpk from sea-star oocytes, nor for cyclic-AMP-dependent protein kinase. These studies point to possible regulation of CKII by protein phosphorylation.
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PMID:Purification and characterization of echinoderm casein kinase II. Regulation by protein kinase C. 159 Jul 72

Early in an infection the bloodstream forms of the African trypanosome Trypanosoma brucei brucei are long, slender and rapidly dividing. Later, non-dividing, short, stumpy forms may be found. In this report we described biochemical differences between the two parasite populations in the phosphorylation of their proteins in vitro. Compared with the slender populations, the non-dividing stumpy forms of the parasites exhibit decreased phosphorylation of an 80 kDa protein and enhanced phosphorylation of 37 kDa and 42 kDa proteins (pp37 and pp42). These changes occurred regardless of whether the stumpy trypanosomes were generated naturally during the course of the infection or induced by difluoromethylornithine treatment. The phosphorylation of pp37 and pp42 occurs on serine and threonine residues and is totally dependent upon the presence of Mn2+ or Mg2+. However, excess Mn2+ or Mg2+ inhibits phosphorylation. Maximal phosphorylation of pp42 occurs with 1 mm-Mn2+ or 10 mm-Mg2+, whereas that of pp37 occurs with 50 mM-Mn2+ or greater than 100 mm-Mg2+. The phosphorylation of pp37 is greatly enhanced by KCl, whereas that of pp42 is only slightly increased by this salt. Ca2+, calmodulin, phospholipids and cyclic AMP have no discernible effect upon the phosphorylation of pp42 or pp37 in vitro, whereas heparin, suramin, polylysine, polyarginine and polyamines all inhibit phosphorylation. Thus the enzymes that phosphorylate pp42 and pp37 have properties similar to, but distinct from, those of mammalian casein kinase II. Since the casein-kinase-like activity is higher in the slender than in the stumpy forms, the enhanced phosphorylation of pp42 and pp37 in the non-dividing parasites is probably a result of the enhanced synthesis of these acidic proteins.
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PMID:Phosphorylation differences among proteins of bloodstream developmental stages of Trypanosoma brucei brucei. 201 86

An hepatic protein kinase that phosphorylates microtubule-associated protein 2 (MAP-2) on Ser/Thr residues is markedly activated after intraperitoneal injection of cycloheximide in the rat. The enzyme has been purified greater than 10,000-fold to near homogeneity and corresponds to a 54-kDa polypeptide, based on auto-phosphorylation, renaturation of activity from sodium dodecyl sulfate gels, and gel filtration. The protein kinase activity is unaffected by prior autophosphorylation, Ca2+, diacylglycerol and phospholipids, cyclic nucleotides, staurosporine, and protein kinase inhibitor, but can be totally and specifically deactivated by the Ser/Thr protein phosphatase 2A. The enzyme is inhibited completely but reversible by transition metals and p-chloromercuribenzoate, and is strongly stimulated by poly-L-lysine toward most, but not all protein substrates. The activity of the cycloheximide-stimulated MAP-2 kinase (pp54 MAP-2 kinase) toward potential polypeptide substrates was compared to that of an insulin-stimulated MAP-2 kinase (pp42 MAP-2 kinase). Although both MAP-2 kinases exhibited little or no ability to phosphorylate histones and casein, the two kinases had a distinguishable substrate specificity. At comparable MAP-2 phosphorylating activities, pp42 MAP-2 kinase, but not pp54 MAP-2 kinase, phosphorylated and activated the Xenopus S6 protein kinase II. Moreover, pp42 MAP-2 kinase phosphorylated myelin basic protein at 10-12-fold higher rates than did pp54 MAP-2 kinase. Cycloheximide-activated pp54 MAP-2 protein kinase appears to be a previously uncharacterized protein kinase that is itself regulated through Ser/Thr phosphorylation and, perhaps, polypeptide regulators with basic domains. The identity of the upstream regulatory elements and the native substrates remain to be established.
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PMID:pp54 microtubule-associated protein 2 kinase. A novel serine/threonine protein kinase regulated by phosphorylation and stimulated by poly-L-lysine. 217 Mar 74

Okadaic acid is a potent and specific inhibitor of protein phosphatases 1 and 2A, and is a strong tumor promoter that is not an activator of protein kinase C. Treatment of quiescent cultures of rat fibroblastic 3Y1 cells with okadaic acid induced marked activation of a kinase activity that phosphorylated microtubule-associated protein (MAP) 2 and myelin basic protein, but not histone or casein, in vitro. This activated kinase eluted at approximately 0.15 M NaCl on a DEAE-cellulose column and its apparent molecular mass was determined to be approximately 40 kDa by gel filtration. Detection of the kinase activity in polyacrylamide gels containing substrate proteins after sodium dodecyl sulfate gel electrophoresis revealed that the okadaic-acid-activated kinase activity resided mainly in two closely related polypeptides with apparent molecular mass approximately 40 kDa. The characteristics of this kinase were indistinguishable from those of the mitogen-activated MAP kinase in the same cells. The okadaic-acid-activated MAP kinase was deactivated by protein phosphatase 2A treatment in vitro. These results suggest that MAP kinase is negatively regulated by protein phosphatases 1 and/or 2A in quiescent cells and therefore can be activated by inhibiting these protein phosphatases. Interestingly, the okadaic-acid-induced activation of MAP kinase was transient and epidermal-growth-factor-induced activation was also transient, even in the presence of okadaic acid. These data may imply that protein phosphatases 1 and 2A are not involved in the deactivation of MAP kinase in cells.
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PMID:Okadaic acid activates microtubule-associated protein kinase in quiescent fibroblastic cells. 217 62

A protein kinase, termed microtubule-associated protein (MAP) kinase, which phosphorylates microtubule-associated protein 2 (MAP-2) in vitro and is stimulated 1.5-3-fold in extracts from insulin-treated 3T3-L1 cells has been identified (Ray, L.B., and Sturgill, T.W. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 1502-1506). Here, we describe chromatographic properties of MAP kinase and provide biochemical characterization of the partially purified enzyme. Isolation of the enzyme is facilitated by its unusually high affinity for hydrophobic interaction chromatography matrices. The molecular weight of the partially purified enzyme was determined to be 35,000 by gel filtration chromatography and 37,000 by glycerol gradient centrifugation. MAP kinase activity of chromatographic fractions correlated precisely with the presence of a 40-kDa phosphoprotein detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. MAP kinase has a Km of 7 microM for ATP and does not utilize GTP. Acetyl-CoA carboxylase, ATP citrate-lyase, casein, histones, phosvitin, protamine, and ribosomal protein S6 were all poor substrates relative to MAP-2. The enzyme is inhibited by fluoride and beta-glycerol phosphate but not by heparin. These properties of MAP kinase distinguish it from protein kinases previously described in the literature.
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PMID:Characterization of insulin-stimulated microtubule-associated protein kinase. Rapid isolation and stabilization of a novel serine/threonine kinase from 3T3-L1 cells. 284 41

Some properties of the protein kinase activity associated with neurofilaments isolated from the brain stem and spinal cord of rats have been investigated. The activity had an apparent Km for ATP of 20 microM, a pH optimum of 8.0 and phosphorylated both serine and threonine residues in neurofilament proteins. Cyclic AMP had no effect on the in vitro reaction and casein was a preferred exogenous substrate in comparison to histone. Phosphopeptide mapping of the 145 kDa subunit from neurofilaments phosphorylated in the presence and absence of microtubule proteins indicated that the neurofilament-associated activity was distinct from the microtubule-associated protein kinase. Limited proteolysis of neurofilaments with chymotrypsin indicated that the enzyme activity was not associated with a domain of the 200 kDa subunit which may form the side-arm projections on neurofilaments.
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PMID:Characteristics of the protein kinase activity associated with rat neurofilament preparations. 668 14

The role of the C-terminal domain of CTP: phosphocholine cytidylyltransferase (CT) was explored by the creation of a series of deletion mutations in rat liver cDNA, which were expressed in COS cells as a major protein component. Deletion of up to 55 amino acids from the C-terminus had no effect on the activity of the enzyme, its stimulation by lipid vesicles or on its intracellular distribution between soluble and membrane-bound forms. However, deletion of the C-terminal 139 amino acids resulted in a 90% decrease in activity, loss of response to lipid vesicles and a significant decrease in the fraction of membrane-bound enzyme. Identification of the domain that is phosphorylated in vivo was determined by analysis of 32P-labelled CT mutants and by chymotrypsin proteolysis of purified CT that was 32P-labelled in vivo. Phosphorylation was restricted to the C-terminal 52 amino acids (domain P) and occurred on multiple sites. CT phosphorylation in vitro was catalysed by casein kinase II, cell division control 2 kinase (cdc2 kinase), protein kinases C alpha and beta II, and glycogen synthase kinase-3 (GSK-3), but not by mitogen-activated kinase (MAP kinase). Casein kinase II phosphorylation was directed exclusively to Ser-362. The sites phosphorylated by cdc2 kinase and GSK-3 were restricted to several serines within three proline-rich motifs of domain P. Sites phosphorylated in vitro by protein kinase C, on the other hand, were distributed over the N-terminal catalytic as well as the C-terminal regulatory domain. The stoichiometry of phosphorylation catalysed by any of these kinases was less than 0.2 mol P/mol CT, and no effects on enzyme activity were detected. This study supports a tripartite structure for CT with an N-terminal catalytic domain and a C-terminal regulatory domain comprised of a membrane-binding domain (domain M) and a phosphorylation domain (domain P). It also identifies three kinases as potential regulators in vivo of CT, casein kinase II, cyclin-dependent kinase and GSK-3.
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PMID:Functions of the C-terminal domain of CTP: phosphocholine cytidylyltransferase. Effects of C-terminal deletions on enzyme activity, intracellular localization and phosphorylation potential. 765 14

Increases (5-fold) in the rate of phosphorylation of beta-casein were observed in extracts of human gingival fibroblasts that had been stimulated by interleukin 1 (IL-1) or tumour necrosis factor (TNF). The induced kinase was cytosolic and had little activity on alpha-casein. Its chromatographic behaviour on anion-exchange and gel-filtration columns was similar to that of beta-casein kinase, an enzyme detected originally in MRC-5 cells stimulated by IL-1 and TNF. Phosphopeptide maps of beta-casein confirmed that the kinase activated in gingival fibroblasts had the same substrate specificity as beta-casein kinase. In gingival fibroblasts, beta-casein kinase activity was maximum after 15 min of stimulation by IL-1 or TNF, and remained activated for several hours. Activations of small heat-shock protein (hsp27) kinase and mitogen-activated protein (MAP) kinase were also maximum 15 min after stimulation, but decreased to background levels within the next 30 min. Study of the effects of 21 agents other than IL-1 or TNF showed that none activated beta-casein kinase, whereas several activated MAP kinase or hsp27 kinase. beta-Casein kinase was also detected in extracts of bovine articular chondrocytes and human endothelial cells stimulated by IL-1 or TNF. Semi-purified preparations of fibroblast beta-casein kinase were not inactivated by phosphatases in vitro. Our results suggest that it may be involved in responses specific to IL-1 and TNF in a wide range of cell types and that its activation probably involves mechanisms other than its phosphorylation.
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PMID:Specific activation of beta-casein kinase by the inflammatory cytokines interleukin 1 and tumour necrosis factor. 781 78

We have isolated two closely related cDNA clones (cATPK19 and cATPK6) with homology to protein-serine/threonine kinases from Arabidopsis thaliana using the polymerase chain reaction (PCR). The deduced amino acid sequences of the ATPK19 and ATPK6 contain all 11 conserved regions of the catalytic domain of protein kinases, and have homology to p70 ribosomal S6 kinases (52%). ATPK19 and ATPK6 have putative PEST regions in their N- and C-terminal regions, and these regions also contain putative phosphorylation sites that are recognized by casein kinases or proline-directed protein kinases such as cdc2, MAP kinase, and p54 MAP-2 kinase (SAPK). The transcription levels of the ATPK19 and ATPK6 genes rapidly and markedly increased when plants were subjected to cold or high-salt stresses. These observations suggest that ATPK19 and ATPK6 may function in the adaptation of plant cells to cold or high-salt conditions, providing an understanding of the role of protein phosphorylation in plant responses to environmental stresses.
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PMID:Two genes that encode ribosomal-protein S6 kinase homologs are induced by cold or salinity stress in Arabidopsis thaliana. 782 36


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