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)

Human cytomegalovirus encodes an unusual protein kinase, UL97, which is a member of the HvU(L) family of protein kinases encoded by diverse herpesviruses. UL97 is able to autophosphorylate and to phosphorylate certain exogenous substrates, including nucleoside analogs such as ganciclovir. It has previously been concluded that phosphorylation of UL97 is essential for its phosphorylation of ganciclovir. We examined the relationship between autophosphorylation of UL97 and its activity on exogenous substrates. Glutathione S-transferase-UL97 fusion protein purified from insect cells was found to be already partially phosphorylated, but neither extensive autophosphorylation nor phosphatase treatment meaningfully altered the time course of its phosphorylation of the exogenous substrate, histone H2B. Sequencing and mass spectrometric analyses of (32)P-labeled tryptic peptides of the UL97 fusion protein identified nine sites of autophosphorylation, all within the first 200 residues of the protein, outside of conserved protein kinase subdomains. A peptide corresponding to the N-terminal UL97 segment that was most extensively autophosphorylated was readily phosphorylated by UL97, confirming that fusion protein sequences are not required for phosphorylation at this site. Deletion mutants lacking at least the first 239 residues exhibited drastically reduced autophosphorylation (<5%) but retained near-wild-type H2B phosphorylation activity. Baculoviruses expressing these mutants efficiently directed the phosphorylation of ganciclovir in insect cells. Taken together, these results identify the autophosphorylation sites of a herpesvirus protein kinase and show that autophosphorylation of UL97 is not required for phosphorylation of exogenous substrates.
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PMID:Relationship between autophosphorylation and phosphorylation of exogenous substrates by the human cytomegalovirus UL97 protein kinase. 1241 36

It is known that the level of cGMP is modulated in response to a number of stimuli in plant cells but intracellular events distal to cGMP metabolism are not clear. Cyclic GMP-dependent protein kinase (Pk-G) is a major effector of cGMP action in animals and yeasts. We wanted to determine whether such kinase is present in plant cells. A soluble protein kinase was isolated from seedlings of Pharbitis nil and purified following purification methods including anion-exchange and affinity-chromatography. The enzyme consists of a single polypeptide of M(r) 70 kDa as determined by SDS-PAGE. From conventional modulators only cyclic GMP, when applied in low concentration, was able to accelerate the enzyme activity in the presence of histones. The enzyme autophosphorylated on serine and threonine residues and phosphorylated some substrates only on serine residues. Mixture of histones and histones H2B, H3 were the best phosphate acceptors. The process of autophosphorylation was accelerated by a low concentration of cGMP and reduced by high concentration of this second messenger. Antibodies raised against catalytic domain of animals Pk-G I alpha and beta cross-reacted with protein kinase from Pharbitis nil tissue. These data, taken together, demonstrate the presence of functional enzyme, which activity is regulated by cGMP and allow to classify this protein kinase as a member of the second messenger regulated group of enzymes.
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PMID:Biochemical evidence for a cGMP-regulated protein kinase in Pharbitis nil. 1284 35

Approximately 65% of B cells generated in human bone marrow are potentially harmful autoreactive B cells. Most of these cells are clonally deleted in the bone marrow, while those autoreactive B cells that escape to the periphery are anergized or perish before becoming mature B cells. Escape of self-reactive B cells from tolerance permits production of pathogenic auto-antibodies; recent studies suggest that extended B lymphocyte survival is a cause of autoimmune disease in mice and humans. Here we report a mechanism for the regulation of peripheral B-cell survival by serine/threonine protein kinase Cdelta (PKCdelta): spontaneous death of resting B cells is regulated by nuclear localization of PKCdelta that contributes to phosphorylation of histone H2B at serine 14 (S14-H2B). We show that treatment of B cells with the potent B-cell survival factor BAFF ('B-cell-activating factor belonging to the TNF family') prevents nuclear accumulation of PKCdelta. Our data suggest the existence of a previously unknown BAFF-induced and PKCdelta-mediated nuclear signalling pathway which regulates B-cell survival.
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PMID:Regulation of B-cell survival by BAFF-dependent PKCdelta-mediated nuclear signalling. 1536 83

Here we describe and characterize a small serine/threonine kinase (SSTK) which consists solely of the N- and C-lobes of a protein kinase catalytic domain. SSTK protein is highly conserved among mammals, and no close homologues were found in the genomes of nonmammalian organisms. SSTK specifically interacts with HSP90-1beta, HSC70, and HSP70 proteins, and this association appears to be required for SSTK kinase activity. The SSTK transcript was most abundant in human and mouse testes but was also detected in all human tissues tested. In the mouse testis, SSTK protein was localized to the heads of elongating spermatids. Targeted deletion of the SSTK gene in mice resulted in male sterility due to profound impairment in motility and morphology of spermatozoa. A defect in DNA condensation in SSTK null mutants occurred in elongating spermatids at a step in spermiogenesis coincident with chromatin displacement of histones by transition proteins. SSTK phosphorylated histones H1, H2A, H2AX, and H3 but not H2B or H4 or transition protein 1 in vitro. These results demonstrate that SSTK is required for proper postmeiotic chromatin remodeling and male fertility. Abnormal sperm chromatin condensation is common in sterile men, and our results may provide insight into the molecular mechanisms underlying certain human infertility disorders.
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PMID:Identification and characterization of SSTK, a serine/threonine protein kinase essential for male fertility. 1587 Feb 94

The human malaria parasite Plasmodium falciparum contains two nucleosome assembly proteins, which we have termed PfNAPS and PfNAPL. We have over-expressed, purified and characterized these proteins using biochemical and biophysical techniques. PfNAPS and PfNAPL exist as dimers in solution and circular dichroism studies suggest that they may have different three-dimensional protein structures. ELISA-based binding data also suggest that PfNAPS and PfNAPL preferentially interact with the H3-H4 tetramer histones over H2A and H2B histones. We show that the parasite lysate phosphorylates only PfNAPL and this phosphorylation can be inhibited by heparin suggesting a potential role of casein kinase II in this process. Immuno-fluorescence experiments revealed that both PfNAPS and PfNAPL were expressed in all erythrocytic stages of the parasite. PfNAPL was predominantly localised in the cytoplasm in asexual and sexual stages of the parasite. PfNAPS did not co-localise with PfNAPL and was more intimately associated with the parasite nucleus, most strikingly in P. falciparum gametocytes. Taken together, our data show that although PfNAPS and PfNAPL share histone chaperone acitivities, they are regulated differently by phosphorylation and are spatially segregated within the parasite. These proteins are therefore likely to play non-redundant roles as nucleosome assembly motors in the parasite.
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PMID:Biochemical characterization of the two nucleosome assembly proteins from Plasmodium falciparum. 1589 28

Nucleosome assembly protein 1 (NAP1) is conserved from yeast to human and facilitates the in vitro assembly of nucleosomes as a histone chaperone. Inconsistent with their proposed function in the nucleus, however, many NAP1 proteins had been reported to localize in the cytoplasm. We investigated the subcellular localization of tobacco (Nicotiana tabacum) and rice (Oryza sativa) NAP1 family proteins first by identification of interacting partners and by direct examination of the localization of green fluorescent protein-tagged proteins. Through treatment of tobacco cells with leptomycin B and mutagenesis of nuclear export signal, we demonstrated that Nicta;NAP1;1 and Orysa;NAP1;1 shuttle between the cytoplasm and the nucleus. Together with the demonstration that tobacco NAP1 proteins bind histone H2A and H2B, our results support the current model and provide additional evidence that function of NAP1 as histone chaperones appears to be conserved in plants. In addition, we show that tobacco NAP1 proteins interact with tubulin and the mitotic cyclin Nicta;CYCB1;1, suggesting a role for NAP1 in microtubule dynamics. Interestingly, in spite of their high homology with the above NAP1 proteins, the other three tobacco proteins and Orysa;NAP1;2 did not show nucleocytoplasmic shuttling and were localized only in the cytoplasm. Moreover, Orysa;NAP1;3 that lacks a typical nuclear localization signal sequence was localized in both the cytoplasm and the nucleus. Finally, we show that only Orysa;NAP1;3 could be phosphorylated by casein kinase 2alpha in vitro. However, this phosphorylation was not responsible for nuclear import of Orysa;NAP1;3 as being demonstrated through mutagenesis studies. Together, our results provide an important step toward elucidating the molecular mechanism of function of the NAP1 family proteins in plants.
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PMID:Interacting proteins and differences in nuclear transport reveal specific functions for the NAP1 family proteins in plants. 1598 Jan 99

Histone-lysine methylation is linked to transcriptional regulation and the control of epigenetic inheritance. Lysine residues can be mono-, di-, or trimethylated, and it has been suggested that each methylation state of a given lysine may impart a unique biological function. In yeast, histone H3 lysine 4 (K4) is mono-, di-, and trimethylated by the Set1 histone methyltransferase. Previous studies show that Set1 associates with RNA polymerase II and demarcates transcriptionally active genes with K4 trimethylation. To determine whether K4 trimethylation might be selectively regulated, we screened a library of yeast deletion mutants associated with transcriptional regulation and chromatin function. We identified BUR2, a cyclin for the Bur1/2 (BUR) cyclin-dependent protein kinase, as a specific regulator of K4 trimethylation. Surprisingly, BUR also regulated H2B monoubiquitylation, whereas other K4 methylation states and H3 lysine 79 (K79) methylation were unaffected. Synthetic genetic array (SGA) and transcription microarray analyses of a BUR2 mutant revealed that BUR is functionally similar to the PAF, Rad6, and Set1 complexes. These data suggest that BUR acts upstream of these factors to control their function. In support, we show that recruitment of the PAF elongation complex to genes is significantly impaired in a BUR2 deletion. Our data reveal a novel function for the BUR kinase in transcriptional regulation through the selective control of histone modifications.
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PMID:BUR kinase selectively regulates H3 K4 trimethylation and H2B ubiquitylation through recruitment of the PAF elongation complex. 1604 Feb 46

A soybean histone-type protein kinase was used to prepare (32)P-labeled histone H1 as substrate for purification and characterization of a phosphoprotein phosphatase (EC 3.1.3.16) from soybean hypocotyls. The phosphatase has been purified 169-fold by ammonium sulfate fractionation, ethanol precipitation, and chromatography on Sephadex G-150, DEAE-Sephadex A-25 and Sephadex G-100. The activity of the phosphoprotein phosphatase is distinct from that of acid and alkaline phosphatases (EC 3.1.3.1) as well as from that of nucleotidases. The final enzyme preparation does not contain histone protease activity, although it can be detected during the early stages of purification. The protease(s) apparently can attack phosphorylated histone H1, indicating that phosphorylation does not protect the protein against proteolytic degradation.The amounts of (32)P released from [(32)P]histone H1 are proportionally recovered as [(32)P]Pi, indicating that the dephosphorylation is due to the action of phosphoprotein phosphatase. The enzyme shows maximal activity at pH 7 to 8 and has a specific activity of 19 nanomoles of [(32)P]Pi released from [(32)P]histone H1 per minute per milligram of protein. The apparent K(m) for phosphohistone H1 is 4.0 +/- 0.4 micromolar. The estimated molecular weight of the enzyme is approximately 30,000 by gel filtration. The enzyme activity does not depend upon the addition of reducing agent and metal ion. Zn(2+), Co(2+), NaF, pyrophosphate, or ATP at 1 millimolar, however, inhibits the enzyme activity by about 70%. The enzyme activity is unaffected by cyclic nucleotides and plant growth substances but is inhibited by polyamines. All the phosphorylated histone species and protamine, not low molecular weight phosphoesters, act as competitive inhibitors for the dephosphorylation of [(32)P]histone H1.Besides its action on phosphohistone H1, the soybean enzyme also catalyzes the dephosphorylation of other phosphohistone species (H2A, H2B, H3, and H4), degraded phosphohistone H1, and possibly phosphorylated casein and phosvitin. All these results indicate that the enzyme is a nonspecific phosphoprotein phosphatase.
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PMID:Phosphoprotein Phosphatase of Soybean Hypocotyls: PURIFICATION, PROPERTIES, AND SUBSTRATE SPECIFICITIES . 1666 38

In Saccharomyces cerevisiae, the evolutionarily conserved nucleocytoplasmic shuttling protein Nap1 is a cofactor for the import of histones H2A and H2B, a chromatin assembly factor and a mitotic factor involved in regulation of bud formation. To understand the mechanism by which Nap1 function is regulated, Nap1-interacting factors were isolated and identified by mass spectrometry. We identified several kinases among these proteins, including casein kinase 2 (CK2), and a new bud neck-associated protein, Nba1. Consistent with our identification of the Nap1-interacting kinases, we showed that Nap1 is phosphorylated in vivo at 11 sites and that Nap1 is phosphorylated by CK2 at three substrate serines. Phosphorylation of these serines was not necessary for normal bud formation, but mutation of these serines to either alanine or aspartic acid resulted in cell cycle changes, including a prolonged S phase, suggesting that reversible phosphorylation by CK2 is important for cell cycle regulation. Nap1 can shuttle between the nucleus and cytoplasm, and we also showed that CK2 phosphorylation promotes the import of Nap1 into the nucleus. In conclusion, our data show that Nap1 phosphorylation by CK2 appears to regulate Nap1 localization and is required for normal progression through S phase.
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PMID:Phosphorylation by casein kinase 2 regulates Nap1 localization and function. 1808 83

The mammalian adenosine monophosphate-activated protein kinase (AMPK) is a serine-threonine kinase protein complex that is a central regulator of cellular energy homeostasis. However, the mechanisms by which AMPK mediates cellular responses to metabolic stress remain unclear. We found that AMPK activates transcription through direct association with chromatin and phosphorylation of histone H2B at serine 36. AMPK recruitment and H2B Ser36 phosphorylation colocalized within genes activated by AMPK-dependent pathways, both in promoters and in transcribed regions. Ectopic expression of H2B in which Ser36 was substituted by alanine reduced transcription and RNA polymerase II association to AMPK-dependent genes, and lowered cell survival in response to stress. Our results place AMPK-dependent H2B Ser36 phosphorylation in a direct transcriptional and chromatin regulatory pathway leading to cellular adaptation to stress.
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PMID:Signaling kinase AMPK activates stress-promoted transcription via histone H2B phosphorylation. 2081 44


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