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

---

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 Ste20p protein kinase was immunopurified from yeast cells and analyzed in an in vitro assay system. Ste20p immune complexes exhibited autophosphorylating activity at serine and threonine residues and specifically phosphorylated a bacterially expressed glutathione S-transferase (GST) fusion of Ste11p (a mitogen-activated protein or extracellular signal-regulated kinase kinase (MEK) kinase homologue) at serine and threonine residues. In contrast, GST fusions either of Ste7p (a MEK homologue) or the beta-subunit of the mating response G-protein and immunoprecipitated Ste5p were not phosphorylated by the Ste20p immune complexes. Myelin basic protein was identified as an excellent in vitro substrate, whereas histone H1 was only poorly phosphorylated. Evidence was obtained that autophosphorylation might play a regulatory role for the in vitro kinase activity. The in vitro activity was found to be Ca(2+)-independent. Both the in vivo and in vitro activities were abolished by mutational changes of either the conserved lysine residue 649 within the ATP binding site or threonine 777 between the catalytic subdomains VII and VIII. Wild-type Ste20p and the catalytically inactive T777A mutant were identified as phosphoproteins in vivo. The phosphorylation occurred at serine and threonine residues independent of pheromone stimulation. Based on the genetically determined significance of Ste20p in pheromone signal transduction and on our in vitro studies, we propose the model that Ste20p represents a yeast MEK kinase kinase whose function is to link G-protein-coupled receptors through G beta gamma to a mitogen-activated protein kinase module.
...
PMID:Molecular characterization of Ste20p, a potential mitogen-activated protein or extracellular signal-regulated kinase kinase (MEK) kinase kinase from Saccharomyces cerevisiae. 760 57

A unique and highly conserved structural feature of approximately 90-kDa ribosomal S6 kinase (p90rsk or RSK) is the presence of two non-identical kinase domains. To explore the mechanism of RSK activation, a cloned human RSK cDNA (RSK3) was used to generate and characterize several site-directed RSK mutants; K91A (N-Lys, NH2-terminal ATP-binding mutant), K444A (C-Lys, COOH-terminal ATP-binding mutant), N/C-Lys (double ATP-binding mutant) T570A (C-Thr, mutant of the putative MAPK phosphorylation site in subdomain VIII of the C-domain), S218A (N-Ser, mutant of the corresponding NH2-terminal residue). Epitope-tagged RSKs were expressed in transfected COS cells followed by immunoprecipitation with or without prior in vivo epidermal growth factor stimulation. Kinase activity (S6 peptide) of N/C-Lys and N-Lys was ablated (and partially impaired with N-Ser). In contrast, both C-Lys and C-Thr retained high levels of kinase activity and were capable of responding to stimulation. C-Lys also retained partial kinase activity toward other substrates (c-Fos, S40 ribosomes, protein phosphatase 1 G-subunit, histones, and Leu-Arg-Arg-Ala-Ser-Leu-Gly (Kemptide)) whereas N-Lys did not. The isolated NH2-and COOH-terminal domains were also expressed; the C-domain was inactive, whereas the N-domain retained partial activity. Relative to wild-type, both N-Lys and C-Lys (as well as N-Ser and C-Thr) underwent partial in vitro autophosphorylation that was further stimulated by EGF protein tyrosine phosphatase. We conclude that 1) the NH2-terminal RSK kinase domain mediates substrate phosphorylation; 2) both domains contribute to autophosphorylation; 3) the putative MAPK phosphorylation site is not required for growth factor-stimulated autophosphorylation or kinase activation.
...
PMID:Divergent functional roles for p90rsk kinase domains. 764 38

A putative mitogen-activated protein kinase (MAPK) has recently been identified, which potentially phosphorylates the human epidermal growth factor (EGF) receptor at a physiological site (Thr-669) and is distinguished from other MAPKs/extracellular signal-regulated protein kinases (ERKs) on the basis of chromatographic, immunological, and kinetic data. Here we report that this newly discovered MAPK is physically associated with the EGF receptor in A431 cells and with the related receptor/tyrosine kinase HER2 (encoded by c-neu) in enzyme preparations obtained from Wilm's tumors. This human EGF receptor-associated kinase is characterized as a 40-kDa Thr-669 kinase that exists in a high molecular mass complex with the respective growth factor receptor. EGF treatment of A431 cells stimulates the tyrosine phosphorylation of p40 and increases Thr-669 kinase activity in p40-containing fractions. The 40-kDa kinase is recognized by affinity-purified polyclonal antibodies directed against the sea star p44mpk and a Pan-ERK antibody directed against the conserved subdomain VIII of MAPKs/ERKs, but is not recognized by antibodies selective for the rat p44erk1 and/or the p42mapk/erk2 isoforms, thus identifying the EGF receptor-associated kinase as a novel MAPK that may regulate receptor function in vivo.
...
PMID:Identification of a human epidermal growth factor receptor-associated protein kinase as a new member of the mitogen-activated protein kinase/extracellular signal-regulated protein kinase family. 768 42

The mitogen activated protein (MAP) kinase pathway of eukaryotes is stimulated by many growth factors and is required for the integration of multiple cellular signals. In order to study the function of MAP kinases during plant ovule development we have synthesized a Petunia hybrida ovule-specific cDNA library and screened for MAP protein kinase-related sequences using a DNA probe obtained by PCR. A full-length cDNA clone was identified (PMEK for Petunia hybrida MAP/ERK-related protein kinase) and shown to encode a protein related to the family of MAP/ERK protein kinases. Southern blot analysis showed that PMEK is a member of a small multigene family in P. hybrida. The cDNA codes for a protein (PMEK1) of 44.4 kDa with an overall sequence identity of 44% to the products of the mammalian ERK/MAP kinase gene, and the budding yeast KSS1 and FUS3 genes. PMEK1 displays 96 and 80% identity respectively with the tobacco NTF3 and Arabidopsis ATMPK1 kinases, and only 50% to the more distantly related plant MAP kinase MsERK1 from alfalfa. The two phosphorylation sites found in the loop between subdomain VII and VIII in all the other MAP kinases are also present in PMEK1. RNA gel blot and RT-PCR analyses demonstrated that PMEK1 is expressed in vegetative organs and preferentially accumulated in female reproductive organs of P. hybrida. In situ hybridization experiments showed that in the reproductive organs PMEK1 is expressed only in the ovary and not in the stamen.
...
PMID:A homologue of the MAP/ERK family of protein kinase genes is expressed in vegetative and in female reproductive organs of Petunia hybrida. 788 23

We have identified a putative protein kinase gene from both Plasmodium falciparum cDNA and genomic DNA libraries. The nucleotide sequence contains an open-reading frame of 2646 bp, which codes for a predicted protein of 882 amino acid residues. Comparison of the predicted amino acid sequence with those in GenBank suggests that this gene codes for a protein similar to the mitogen-activated protein (MAP) kinase of other organisms. This MAP kinase-related protein, named PfMRP, contains the TDY dual phosphorylation site upstream of the highly conserved VATRWYRAPE sequence in subdomain VIII. PfMRP contains an unusually large and highly charged domain within its carboxyl-terminal segment, which includes two repetitive sequences of either a tetrapeptide or octapeptide motif. PfMRP gene is located on chromosome 14. Northern blot analysis of total RNA reveals the presence of a single mRNA transcript approximately 4.2 kb in length, which is predominantly expressed in gametocytes and gametes/zygotes.
...
PMID:Stage-specific expression of a Plasmodium falciparum protein related to the eukaryotic mitogen-activated protein kinases. 881 78

Using a combination of screening, RACE, and RT-PCR, we have isolated a new rat brain cDNA, we refer to as rMNK2, that showed strong homology to known MAP-kinases. The deduced amino acid sequence of rMNK2 indicated that it is the rat homolog of human p63(mapk), showing 94.5% identity. rMNK2 showed 77% homology with rat ERK3 and its human homolog p97(mapk), and 43% homology with both rat genes rMNK1(ERK1) and ERK2, within the kinase domain. This suggest that rMNK2 and ERK3 belong to a separate subfamily within the rat MAP-kinase multigene family. The most interesting difference lies in subdomain VIII, where this new subfamily contain a SEG/SPR motif instead of the TEY/APE found in the ERK subfamily, the TPY/APE found in the JNK/SAPK subfamily or the TGY/APE found in the p38/RK subfamily. The human homologs of ERK3 and rMNK2 (p97(mapk) and p63(mapk)) also show this significant change. Expression of rMNK2 has been detected in brain and to a lesser extent in lung by reverse transcription/PCR (RT-PCR). In situ hybridization of rat brain slices demonstrated a restricted expression of rMNK2 in the choroid plexus and hippocampus. This is interesting because the human homolog p63(mapk) maps to 18q12-21, a region that might be implicated in manic-depressive illness.
...
PMID:Isolation of a cDNA encoding the rat MAP-kinase homolog of human p63mapk. 887 88

The 78-kDa protein kinase Mekk1 plays an important role in the stress response pathway that involves the activation of downstream kinases Sek1 and stress-activated protein kinase/c-Jun NH2-terminal kinase. Conserved serine and threonine residues located between the kinase subdomains VII and VIII of many protein kinases are phosphorylated for maximal kinase activation. Two threonine residues within this region in Mekk1 at positions 560 and 572, but not the serine at 557, were shown to be essential for catalytic activity in this study. When these threonine residues were replaced with alanine, there was a significant loss in phosphotransferase activity toward the primary substrate, Sek1, and a large decrease in autophosphorylation activity. Site-directed mutagenesis demonstrated that these threonine residues cannot be replaced with either serine or glutamic acid for preservation of phosphotransferase activity. Further examination of the Mekk1 mutants isolated from 32P-labeled transfected COS cells showed that Thr-560 and Thr-572 were indeed phosphorylated after two-dimensional tryptic-chymotryptic phosphopeptide analysis. Additional determinants in the NH2-terminal domain of Mekk1 also play a role in the regulation of Mekk1 activity. Although Pak3 and PKC can activate Mekk1 in vivo, this interaction is indirect and independent, since there was no direct phosphorylation of Mekk1 by Pak3 or PKC or of Pak3 by PKC, respectively.
...
PMID:Identification of two essential phosphorylated threonine residues in the catalytic domain of Mekk1. Indirect activation by Pak3 and protein kinase C. 906 12

MEK kinase 1 (MEKK1) shares sequence identity with the yeast kinases Ste11 and Byr2, and is capable of phosphorylation and activation of both mitogen-activated protein/extracellular signal-related protein kinase (MAP/ERK) kinase (MEK) and stress-activated protein kinase (SAPK)/ERK kinase (SEK) in vitro. In vivo, however, MEKK1 predominantly activates the SEK/SAPK kinase cascade. Mechanisms of activation of MEKK1 are unclear. We have identified a major site of autophosphorylation (Thr-575) within the 'activation loop' of MEKK1 between the kinase subdomains VII and VIII. Phosphatase treatment of a constitutively active MEKK1 decreased kinase activity by 59%. Dephosphorylated T575 was rapidly re-(auto)phosphorylated by MEKK1. Mutation of T575 to alanine decreased MEKK1 transphosphorylation activity with a SEK substrate to approx. 30% of wild-type. Mutation of a second threonine residue (Thr-587) to alanine eliminated the phosphorylation of MEK or SEK substrate but not autophosphorylation. MEKK1 autophosphorylation is an intramolecular reaction because active MEKK1 cannot transphosphorylate a kinase-inactive MEKK1. Inactive MEKK1 was not phosphorylated on Thr-575 within cells, suggesting that the phosphorylation of Thr-575 in vivo results from autophosphorylation rather than phosphorylation by an upstream kinase. Autoactivation of MEKK1 via autophosphorylation of Thr-575 might be an immediate response to initial kinase activation through non-phosphorylation mechanisms.
...
PMID:Regulation of the activity of MEK kinase 1 (MEKK1) by autophosphorylation within the kinase activation domain. 907 60

TrkC is a receptor tyrosine kinase that binds neurotrophin-3 (NT-3) with high affinity. A number of naturally occurring splice variants of TrkC exist, including one (TrkC kil4) with a 14 amino acid insertion between subdomains VII and VIII of the tyrosine kinase domain. This kinase insert blocks the ability of NT-3 to stimulate neurite outgrowth in PC12 cells and proliferation in fibroblasts. The inserts also block the ability of TrkC to form a high-affinity complex with Shc and phospholipase C gamma (PLC gamma) and the activation of PtdIns 3-kinase, and attenuates the sustained activation of mitogen-activated protein kinase (MAPK). In the current study we set out to determine whether the attenuation of the activation of MAPK by the insert was the result of the inability of TrkC to activate the Shc-Ras pathway, PtdIns 3-kinase activation, PLC gamma activation, or a combination thereof. Experiments with the use of cell-permeant inhibitors argue against a major role for PLC gamma and PtdIns 3-kinase in the activation of MAPK by TrkC. The introduction of the 14 amino acid kinase insert appeared to slow the kinetics of NT-3-stimulated Shc phosphorylation and Shc-Grb2 association and reduce their magnitude; an effect which was associated with a delayed, and only transient, activation of MAPK. Taken together, our data suggest that the apparent defect in MAPK activation caused by the kinase insert may result predominantly from an inhibition of high-affinity Shc binding, although a role for PLC gamma and PtdIns 3-kinase cannot be completely excluded.
...
PMID:Analysis of mitogen-activated protein kinase activation by naturally occurring splice variants of TrkC, the receptor for neurotrophin-3. 907 61

Several mitogen-activated protein kinase (MAPK) cascades have been identified in eukaryotic cells. The activation of MAPKs is carried out by distinct MAPK kinases (MEKs or MKKs), and individual MAPKs have different substrate preferences. Here we have examined how amino acid sequences encompassing the dual phosphorylation motif located in the loop 12 linker (L12) between kinase subdomains VII and VIII and the length and amino acid sequence of L12 influence autophosphorylation, substrate specificity, and upstream kinase selectivity for the MAPK p38. Conversion of L12 of p38 to an "ERK-like" structure was accomplished in several ways: (i) by replacing glycine with glutamate in the dual phosphorylation site, (ii) by placing a six-amino acid sequence present in L12 of ERK (but absent in p38) into p38, and (iii) by mutations of amino acid residues in loop 12. Two predominant effects were noted: (i) the Xaa residue in the dual phosphorylation motif Thr-Xaa-Tyr as well as the length of L12 influence p38 substrate specificity, and (ii) the length of L12 plays a major role in controlling autophosphorylation. In contrast, these modifications do not result in any change in the selection of p38 by individual MAPK kinases.
...
PMID:Structure-function studies of p38 mitogen-activated protein kinase. Loop 12 influences substrate specificity and autophosphorylation, but not upstream kinase selection. 911 Oct 4


1 2 3 4 5 6 Next >>

---