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)

Reversible phosphorylation of chl a/b protein complex II (LHCII), the mobile light-harvesting antenna, regulates its association and energy transfer/dissipation to photosystem (PS) II or I (state transition). Excitation of LHCII induces conformational changes affecting the exposure of the phosphorylation site at the N-terminal domain to protein kinase(s) [Zer, H., et al. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 8277-8282; Zer, H., et al. (2003) Biochemistry 42, 728-738]. Thus, it was of interest to examine whether the pigment composition of LHCII affects the light-induced modulation of LHCII phosphorylation and state transition. To this end, we have used thylakoids of wild-type Chlamydomonas reinhardtii and xanthophyll deficient mutants npq1, lor1, npq2, npq1 lor1, and npq2 lor1. Phosphorylated protein bands P11, P13, and P17 are considered components of the mobile C. reinhardtii LHCII complex. The protein composition of these bands has been analyzed by mass spectrometry using Qtof-2 with a nanospray attachment. P11 and P13 contain C. reinhardtii light-harvesting chlorophyll a/b binding protein LhcII type I. P17 contains C. reinhardtii LhcII types III and IV. Illumination of isolated thylakoids inhibits the redox-controlled phosphorylation of polypeptide bands P13 and P17 and to a lower extent that of P11. The light-induced inhibition of LHCII phosphorylation and the state transition process are not influenced by extensive differences in the xanthophyll composition of the mutants. Thus, LHCII can be visualized as possessing two functionally distinct, independent domains: (i) the pigment binding transmembrane domain regulating the extent of energy transfer/dissipation and (ii) the surface-exposed phosphorylation site regulating the association of LHCII with PSII or PSI.
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PMID:Light-modulated exposure of the light-harvesting complex II (LHCII) to protein kinase(s) and state transition in Chlamydomonas reinhardtii xanthophyll mutants. 1519 25

A cytochrome b (6) f deficient mutant of Lemna perpusilla maintains a constant and lower level of the light-harvesting chl a/b-binding protein complex II (LHC II) as compared to the wild type plants at low-light intensities. Inhibition of the plastoquinone pool reduction increases the LHC II content of the mutant at both low- and high-light intensities but only at high-light intensity in the wild type plants. Proteolytic activity against LHC II appears during high-light photoacclimation of wild type plants. However, the acclimative protease is present in the mutant at both light intensities. These and additional results suggest that the plastoquinone redox state serves as the major signal-transducing component in the photoacclimation process affecting both, synthesis and degradation of LHC II and appearance of acclimative LHC II proteolysis. The plastoquinol pool cannot be oxidized by linear electron flow in the mutant plants which are locked in a 'high light' acclimation state. The cytochrome b (6) f complex may be involved indirectly in the regulation of photoacclimation via 1) regulation of the plastoquinone redox state; 2) regulation of the redox-controlled thylakoid protein kinase allowing exposure of the dephosphorylated LHC II to acclimative proteolysis.
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PMID:The redox state of the plastoquinone pool controls the level of the light-harvesting chlorophyll a/b binding protein complex II (LHC II) during photoacclimation. 1622 39

Mutants with defects in the cytochrome (cyt) b6/f complex were analyzed for their effect on the expression of a subgroup of nuclear genes encoding plastid-localized enzymes participating in chlorophyll biosynthesis. Their defects ranged from complete loss of the cytb6/f complex to point mutations affecting specifically the quinone-binding QO site. In these seven mutants, light induction of the tetrapyrrole biosynthetic genes was either abolished or strongly reduced. In contrast, a normal induction of chlorophyll biosynthesis genes was observed in mutants with defects in photosystem II, photosystem I, or plastocyanin, or in wild-type cells treated with 3-(3'4'-dichlorophenyl)-1,1-dimethylurea or 2,5-dibromo-3-methyl-6-isopropyl benzoquinone. We conclude that the redox state of the plastoquinone pool does not control light induction of these chlorophyll biosynthetic genes. The signal that affects expression of the nuclear genes appears to solely depend on the integrity of the cytb6/f complex QO site. Since light induction of these genes in Chlamydomonas has recently been shown to involve the blue light receptor phototropin, the results suggest that cytb6/f activity regulates a plastid-derived factor required for their expression. This signaling pathway differs from that which regulates state transitions, since mutant stt7, lacking a protein kinase involved in phosphorylation of the light-harvesting complex II, was not altered in the expression of the chlorophyll biosynthetic genes.
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PMID:Defects in the cytochrome b6/f complex prevent light-induced expression of nuclear genes involved in chlorophyll biosynthesis. 1667 22

The mechanism of induction of apoptosis by dolichyl phosphate (Dol-P) was investigated in U937 cells. Studies using isolated mitochondria revealed that the respiratory complex II activity was almost completely inhibited by 20 microg/ml of Dol-P but not by the same concentration of dolichol. Activities of complex I and III were also inhibited by Dol-P, but nearly 50% of activity still remained at 20 microg/ml. Dol-P induced release of cytochrome-c from the isolated mitochondria. Fluorometric microtiter plate assay revealed that generation of reactive oxygen species (ROS) increased in a time-dependent manner. Flow cytometric analysis also indicated that Dol-P caused loss of mitochondrial membrane potential (Deltapsi(m)) and increased ROS generation. The addition of the antioxidant pyrrolidine dithiocarbamate (PDTC) significantly inhibited Dol-P-induced ROS generation and activation of caspase-3. A specific inhibitor of respiratory complex II, thenoyltrifluoroacetone (TTFA), increased ROS generation, potentially mimicking the consequence of inhibition of electron flow at complex II by Dol-P in U937 cells. Electron microscopy revealed that mitochondria became swollen and spherical in shape by the treatment with Dol-P. Neither the tyrosine kinase inhibitor k252a nor mitogen activated protein kinase/extracellular signal-regulated kinase kinase (MEK) inhibitors PD98059 and U0126 inhibited the Dol-P-induced apoptosis. Together, these results suggest that the direct disruption of mitochondrial respiratory complexes and the consequent ROS generation play a critical role in the initiation of Dol-P-induced apoptosis.
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PMID:Generation of reactive oxygen species is an early event in dolichyl phosphate-induced apoptosis. 1692 72

Trimeric tumor necrosis factor (TNF) binding leads to recruitment of TRADD to TNFR1. In current models, TRADD recruits RIP, TRAF2, and FADD to activate NF-kappaB, Jun N-terminal protein kinase (JNK), and apoptosis. Using stable short-hairpin RNA (shRNA) knockdown (KD) cells targeting these adaptors, TNF death-inducing signaling complex immunoprecipitation demonstrates competitive binding of TRADD and RIP to TNFR1, whereas TRAF2 recruitment requires TRADD. Analysis of KD cells indicates that FADD is necessary for Fas-L- or TRAIL- but not TNF-induced apoptosis. Interestingly, TRADD is dispensable, while RIP is required for TNF-induced apoptosis in human tumor cells. TRADD is required for c-Jun phosphorylation upon TNF exposure. RIP KD abrogates formation of complex II following TNF exposure, whereas TRADD KD allows efficient RIP-caspase 8 association. Treatment with TRAIL also induces formation of a complex II containing FADD, RIP, IKKalpha, and caspase 8 and 10, leading to activation of caspase 8. Our data suggest that TNF triggers apoptosis in a manner distinct from that of Fas-L or TRAIL.
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PMID:Distinct signaling pathways in TRAIL- versus tumor necrosis factor-induced apoptosis. 1694 Jan 86

Recent evidence suggests that unscheduled cell cycle activity leads to neuronal cell death. 3-Nitropropionic acid (3-NP) is an irreversible inhibitor of succinate dehydrogenase and induces cell death in both striatum and cerebral cortex. Here we analyzed the involvement of aberrant cell cycle progression in 3-NP-induced cell death in these brain regions. 3-NP reduced the level of cyclin-dependent kinase inhibitor p27 in striatum but not in cerebral cortex. 3-NP also induced phosphorylation of retinoblastoma protein, a marker of cell cycle progression at late G(1) phase, only in striatum. Pharmacological experiments revealed that cyclin-dependent kinase activity and N-methyl-d-aspartate (NMDA) receptor were cooperatively involved in cell death by 3-NP in striatal neurons, whereas only NMDA receptor was involved in 3-NP-induced neurotoxicity in cortical neurons. Death of striatal neurons was preceded by elevation of somatic Ca(2+) and activation of calpain, a Ca(2+)-dependent protease. Both striatal p27 down-regulation and cell death provoked by 3-NP were dependent on calpain activity. Moreover, transfection of p27 small interfering RNA reduced striatal cell viability. In cortical neurons, however, there was no change in somatic Ca(2+) and calpain activity by 3-NP, and calpain inhibitors were not protective. These results suggest that 3-NP induces aberrant cell cycle progression and neuronal cell death via p27 down-regulation by calpain in striatum but not in the cerebral cortex. This is the first report for differential involvement of cell cycle reactivation in different brain regions and lightens the mechanism for region-selective vulnerability in human disease, including Huntington disease.
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PMID:Differential involvement of cell cycle reactivation between striatal and cortical neurons in cell death induced by 3-nitropropionic acid. 1818 90

The influence of dibromothymoquinone on chlorophyll fluorescence was studied in Chlamydomonas reinhardtii cells using PAM and PEA fluorometers. The reagent affected differently control cells incubated in complete medium and S-starved cells. Thus, the fluorescence yield in the control essentially increased in the presence of dibromothymoquinone, which can be due to the inactivation of light-harvesting complex II protein kinase, followed by the suppression of membrane transition from high-fluorescence state 1 to low-fluorescence state 2. On the contrary, S-starved cells with membranes in state 2 showed a lower fluorescence yield in the presence of dibromothymoquinone than without it. The JIP test of OJIP fluorescence transients suggests that dibromothymoquinone inhibits both light-harvesting complex II kinase and photosynthetic electron transport when added to control, while in starved cells, it acts predominantly as an electron acceptor.
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PMID:[Effect of dibromothymoquinone on chlorophyll a fluorescence in Chlamydomonas reinhardtii cells incubated in complete or sulfur-depleted medium]. 1895 6

Higher plant thylakoid membranes contain a protein kinase that phosphorylates certain threonine residues of light-harvesting complex II (LHCII), the main light-harvesting antenna complexes of photosystem II (PSII) and some other phosphoproteins (Allen, Biochim Biophys Acta 1098:275, 1992). While it has been established that phosphorylation induces a conformational change of LHCII and also brings about changes in the lateral organization of the thylakoid membrane, it is not clear how phosphorylation affects the dynamic architecture of the thylakoid membranes. In order to contribute to the elucidation of this complex question, we have investigated the effect of duroquinol-induced phosphorylation on the membrane ultrastructure and the thermal and light stability of the chiral macrodomains and of the trimeric organization of LHCII. As shown by small angle neutron scattering on thylakoid membranes, duroquinol treatment induced a moderate (~10%) increase in the repeat distance of stroma membranes, and phosphorylation caused an additional loss of the scattering intensity, which is probably associated with the partial unstacking of the granum membranes. Circular dichroism (CD) measurements also revealed only minor changes in the chiral macro-organization of the complexes and in the oligomerization state of LHCII. However, temperature dependences of characteristic CD bands showed that phosphorylation significantly decreased the thermal stability of the chiral macrodomains in phosphorylated compared to the non-phosphorylated samples (in leaves and isolated thylakoid membranes, from 48.3 degrees C to 42.6 degrees C and from 47.5 degrees C to 44.3 degrees C, respectively). As shown by non-denaturing PAGE of thylakoid membranes and CD spectroscopy on EDTA washed membranes, phosphorylation decreased by about 5 degrees C, the trimer-to-monomer transition temperature of LHCII. It also enhanced the light-induced disassembly of the chiral macrodomains and the monomerization of the LHCII trimers at 25 degrees C. These data strongly suggest that phosphorylation of the membranes considerably facilitates the heat- and light-inducible reorganizations in the thylakoid membranes and thus enhances the structural flexibility of the membrane architecture.
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PMID:Effect of phosphorylation on the thermal and light stability of the thylakoid membranes. 1903 44

Thylakoid-soluble phosphoprotein of 9 kDa, TSP9, is an intrinsically unstructured plant-specific protein [Song, J., et al. (2006) Biochemistry 45, 15633-15643] with unknown function but established associations with light-harvesting proteins and peripheries of both photosystems [Hansson, M., et al. (2007) J. Biol. Chem. 282, 16214-16222]. To investigate the function of this protein, we used a combination of reverse genetics and biochemical and fluorescence measurement methods in Arabidopsis thaliana. Differential gene expression analysis of plants with a T-DNA insertion in the TSP9 gene using an array of 24000 Arabidopsis genes revealed disappearance of high light-dependent induction of a specific set of mostly signaling and unknown proteins. TSP9-deficient plants had reduced levels of in vivo phosphorylation of light-harvesting complex II polypeptides. Recombinant TSP9 was phosphorylated in light by thylakoid membranes isolated from the wild-type and mutant plants lacking STN8 protein kinase but not by the thylakoids deficient in STN7 kinase, essential for photosynthetic state transitions. TSP9-lacking mutant and RNAi plants with downregulation of TSP9 showed reduced ability to perform state transitions. The nonphotochemical quenching of chlorophyll fluorescence at high light intensities was also less efficient in the mutant compared to wild-type plants. Blue native electrophoresis of thylakoid membrane protein complexes revealed that TSP9 deficiency increased relative stability of photosystem II dimers and supercomplexes. It is concluded that TSP9 regulates plant light harvesting acting as a membrane-binding protein facilitating dissociation of light-harvesting proteins from photosystem II.
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PMID:Intrinsically unstructured phosphoprotein TSP9 regulates light harvesting in Arabidopsis thaliana. 1911 38

In an experiment with rats system and intracellular energy metabolism was assessed by cell reactions to chronic injection of beta-guanidine propionic acid (beta-GPA) stimulating AMP-dependent protein kinase (AMPK). Suspension was shown to inhibit the succinate dehydrogenase (SDH) activity, reduce glycogen in both types of muscle fibers, and stimulate the activity of alpha-glycerophosphate dehydrogenase (alpha-GPDH) in fast fibers. Supplementing the rat chow with beta-GPA did not modify these parameters during suspension; however, the blood urea level increased considerably in the suspended and control rats. In the controls, beta-GPA as well as suspension, stimulates growth of the aspartate aminotranspherase activity (AST) in blood. Yet, the suspension and beta-GPA injection had no additive effect. Moreover, their effects were opposite in rats subjected to suspension + beta-GPA. Glucose concentration was observed to become lowered in blood of resting rats treated with beta-GPA. This effect can be associated with a more intensive insulin-dependent glucose transport to muscles. The additional glucose, because of increased demand by fibers, underwent to oxidation and did not replenish the intracellular carbohydrate deposits These data suggest energy metabolism shifting toward activation of the processes of disintegration of substrates for energy production due to a sharp growth of energy demand.
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PMID:[Effects of creatine phosphokinase competitive inhibitor on system and tissue energy metabolism in rats in the norm and during unloading]. 1914 Apr 71


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