| 11. |
- Aslani, Alireza, 1965, et al.
(författare)
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ATP-dependent unwinding of a minimal origin of DNA replication by the origin-binding protein and the single-strand DNA-binding protein ICP8 from herpes simplex virus type I.
- 2002
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Ingår i: The Journal of biological chemistry. - 0021-9258. ; 277:43, s. 41204-12
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Tidskriftsartikel (refereegranskat)abstract
- The Herpes simplex virus type I origin-binding protein, OBP, is encoded by the UL9 gene. OBP binds the origin of DNA replication, oriS, in a cooperative and sequence-specific manner. OBP is also an ATP-dependent DNA helicase. We have recently shown that single-stranded oriS folds into a unique and evolutionarily conserved conformation, oriS*, which is stably bound by OBP. OriS* contains a stable hairpin formed by complementary base pairing between box I and box III in oriS. Here we show that OBP, in the presence of the single-stranded DNA-binding protein ICP8, can convert an 80-base pair double-stranded minimal oriS fragment to oriS* and form an OBP-oriS* complex. The formation of an OBP-oriS* complex requires hydrolysable ATP. We also demonstrate that OBP in the presence of ICP8 and ATP promotes slow but specific and complete unwinding of duplex minimal oriS. The possibility that the OBP-oriS* complex may serve as an assembly site for the herpes virus replisome is discussed.
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| 12. |
- Assarsson, Maria, et al.
(författare)
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Restoring proper radical generation by azide binding to the iron site of the E238A mutant R2 protein of ribonucleotide reductase from Escherichia coli.
- 2001
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 276:29, s. 26852-26859
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Tidskriftsartikel (refereegranskat)abstract
- The enzyme activity of Escherichia coli ribonucleotide reductase requires the presence of a stable tyrosyl free radical and diiron center in its smaller R2 component. The iron/radical site is formed in a reconstitution reaction between ferrous iron and molecular oxygen in the protein. The reaction is known to proceed via a paramagnetic intermediate X, formally a Fe(III)-Fe(IV) state. We have used 9.6 GHz and 285 GHz EPR to investigate intermediates in the reconstitution reaction in the iron ligand mutant R2 E238A with or without azide, formate, or acetate present. Paramagnetic intermediates, i.e. a long-living X-like intermediate and a transient tyrosyl radical, were observed only with azide and under none of the other conditions. A crystal structure of the mutant protein R2 E238A/Y122F with a diferrous iron site complexed with azide was determined. Azide was found to be a bridging ligand and the absent Glu-238 ligand was compensated for by azide and an extra coordination from Glu-204. A general scheme for the reconstitution reaction is presented based on EPR and structure results. This indicates that tyrosyl radical generation requires a specific ligand coordination with 4-coordinate Fe1 and 6-coordinate Fe2 after oxygen binding to the diferrous site.
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| 13. |
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Balciunas, Darius, et al.
(författare)
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Functional interactions within yeast mediator and evidence of differential subunit modifications
- 2003
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 278:6, s. 3831-3839
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Tidskriftsartikel (refereegranskat)abstract
- It is possible to recruit RNA polymerase II to a target promoter and, thus, activate transcription by fusing Mediator subunits to a DNA binding domain. To investigate functional interactions within Mediator, we have tested such fusions of the lexA DNA binding domain to Med1, Med2, Gal11, Srb7, and Srb10 in wild type, med1, med2, gal11, sin4, srb8, srb10, and srb11 strains. We found that lexA-Med2 and lexA-Gal11 are strong activators that are independent of all Mediator subunits tested. lexA-Srb10 is a weak activator that depends on Srb8 and Srb11. lexA-Med1 and lexA-Srb7 are both cryptic activators that become active in the absence of Srb8, Srb10, Srb11, or Sin4. An unexpected finding was that lexA-VP16 differs from Gal4-VP16 in that it is independent of the activator binding Mediator module. Both lexA-Med1 and lexA-Srb7 are stably associated with Med4 and Med8, which suggests that they are incorporated into Mediator. Med4 and Med8 exist in two mobility forms that differ in their association with lexA-Med1 and lexA-Srb7. Within purified Mediator, Med4 is present as a phosphorylated lower mobility form. Taken together, these results suggest that assembly of Mediator is a multistep process that involves conversion of both Med4 and Med8 to their low mobility forms.
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| 18. |
- Bambou, Jean-Christophe, et al.
(författare)
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In vitro and ex vivo activation of the TLR5 signaling pathway in intestinal epithelial cells by a commensal Escherichia coli strain.
- 2004
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 279:41, s. 42984-92
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Tidskriftsartikel (refereegranskat)abstract
- The capacity of non-pathogenic enteric bacteria to induce a pro-inflammatory response is under debate in terms of its effect on the symbiosis between the mammalian host and its commensal gut microflora. Activation of NF-kappaB and induction of interleukin-8 (IL-8) and CCL-20 by the commensal Escherichia coli strain MG1655 were first studied in vitro in the human intestinal epithelial cell (IECs) lines HT29-19A and Caco-2, transfected or not with plasmids encoding dominant negative Toll-like receptor (TLR) 5 and myeloid differentiation factor-88 (MyD88) adaptor protein. The response of enterocytes in situ was then assessed using murine ileal biopsies mounted in Ussing chambers. Commensal E. coli induced NF-kappaB DNA binding, NF-kappaB transcriptional activity, CCL-20 expression, and IL-8 secretion in the human IEC lines. E. coli MG1655 flagellin was necessary and sufficient to trigger this pro-inflammatory pathway via its interaction with TLR5 and the subsequent recruitment of the adaptor protein MyD88. Following epithelial cell polarization, signaling could be induced by live E. coli and flagellin on the apical side of HT29-19A. The in vivo relevance of our findings was confirmed, because immunohistochemical staining of murine ileum demonstrated expression of TLR5 in the apical part of enterocytes in situ. Furthermore, flagellin added on the mucosal side of murine ileal biopsies mounted in Ussing chambers induced a basolateral production of KC, a functional murine homolog of human IL-8. These findings provide strong evidence that flagellin released by flagellated commensal bacteria in the intestinal lumen can induce a pro-inflammatory response in enterocytes in vivo.
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| 19. |
- Bandyopadhyay, Gautam, et al.
(författare)
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Glucose activates protein kinase C-zeta /lambda through proline-rich tyrosine kinase-2, extracellular signal-regulated kinase, and phospholipase D : A novel mechanism for activating glucose transporter translocation
- 2001
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Ingår i: J Biol Chem. - 0021-9258. ; 276:38, s. 35537-45
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Tidskriftsartikel (refereegranskat)abstract
- Insulin controls glucose uptake by translocating GLUT4 and other glucose transporters to the plasma membrane in muscle and adipose tissues by a mechanism that appears to require protein kinase C (PKC)-zeta/lambda operating downstream of phosphatidylinositol 3-kinase. In diabetes mellitus, insulin-stimulated glucose uptake is diminished, but with hyperglycemia, uptake is maintained but by uncertain mechanisms. Presently, we found that glucose acutely activated PKC-zeta/lambda in rat adipocytes and rat skeletal muscle preparations by a mechanism that was independent of phosphatidylinositol 3-kinase but, interestingly, dependent on the apparently sequential activation of the dantrolene-sensitive, nonreceptor proline-rich tyrosine kinase-2; components of the extracellular signal-regulated kinase (ERK) pathway, including, GRB2, SOS, RAS, RAF, MEK1 and ERK1/2; and, most interestingly, phospholipase D, thus yielding increases in phosphatidic acid, a known activator of PKC-zeta/lambda. This activation of PKC-zeta/lambda, moreover, appeared to be required for glucose-induced increases in GLUT4 translocation and glucose transport in adipocytes and muscle cells. Our findings suggest the operation of a novel pathway for activating PKC-zeta/lambda and glucose transport.
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| 20. |
- Barnes, Brian R, et al.
(författare)
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The 5'-AMP-activated protein kinase gamma3 isoform has a key role in carbohydrate and lipid metabolism in glycolytic skeletal muscle
- 2004
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 279:37, s. 38441-38447
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Tidskriftsartikel (refereegranskat)abstract
- 5'-AMP-activated protein kinase (AMPK) is a metabolic stress sensor present in all eukaryotes. A dominant missense mutation (R225Q) in pig PRKAG3, encoding the muscle-specific gamma3 isoform, causes a marked increase in glycogen content. To determine the functional role of the AMPK gamma3 isoform, we generated transgenic mice with skeletal muscle-specific expression of wild type or mutant (225Q) mouse gamma3 as well as Prkag3 knockout mice. Glycogen resynthesis after exercise was impaired in AMPK gamma3 knock-out mice and markedly enhanced in transgenic mutant mice. An AMPK activator failed to increase skeletal muscle glucose uptake in AMPK gamma3 knock-out mice, whereas contraction effects were preserved. When placed on a high fat diet, transgenic mutant mice but not knock-out mice were protected against excessive triglyceride accumulation and insulin resistance in skeletal muscle. Transfection experiments reveal the R225Q mutation is associated with higher basal AMPK activity and diminished AMP dependence. Our results validate the muscle-specific AMPK gamma3 isoform as a therapeutic target for prevention and treatment of insulin resistance.
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