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- Grant, MA, et al.
(författare)
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The metal-free and calcium-bound structures of a gamma-carboxyglutamic acid-containing contryphan from Conus marmoreus, glacontryphan-M
- 2004
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 279:31, s. 32464-32473
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Tidskriftsartikel (refereegranskat)abstract
- Glacontryphan-M, a novel calcium-dependent inhibitor of L-type voltage-gated Ca2+ channels expressed in mouse pancreatic beta-cells, was recently isolated from the venom of the cone snail Conus marmoreus (Hansson, K., Ma, X., Eliasson, L., Czerwiec, E., Furie, B., Furie, B. C., Rorsman, P., and Stenflo, J. ( 2004) J. Biol. Chem. 278, 32453-32463). The conserved disulfide-bonded loop of the contryphan family of conotoxins including a D-Trp is present; however, unique to glacontryphan-M is a histidine within the intercysteine-loop and two gamma-carboxy-glutamic acid (Gla) residues, formed by post-translational modification of glutamic acid. The two calcium-binding Gla residues are located in a four residue N-terminal extension of this contryphan. To better understand the structural and functional significance of these residues, we have determined the structure of glacontryphan-M using two-dimensional H-1 NMR spectroscopy in the absence and presence of calcium. Comparisons of the glacontryphan-M structures reveal that calcium binding induces structural perturbations within the Gla-containing N terminus and the Cys(11)-Cys(5)-Pro(6) region of the intercysteine loop. The backbone of N-terminal residues perturbed by calcium, Gla(2) and Ser(3), moves away from the His(8) and Trp(10) aromatic rings and the alignment of the D-Trp(7) and His(8) aromatic rings with respect to the Trp(10) rings is altered. The blockage of L-type voltage-gated Ca2+ channel currents by glacontryphan-M requires calcium binding to N-terminal Gla residues, where presumably histidine and tryptophan may be accessible for interaction with the channel. The backbone Calpha conformation of the intercysteine loop of calcium-bound glacontryphan-M superimposes on known structures of contryphan-R and Vn (0.83 and 0.66 Angstrom, respectively). Taken together these data identify that glacontryphan-M possesses the canonical contryphan intercysteine loop structure, yet possesses critical determinants necessary for a calcium-induced functionally required conformation.
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- Hilson, P., et al.
(författare)
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Versatile gene-specific sequence tags for Arabidopsis functional genomics : Trancript profiling and reverse genetics applications
- 2004
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Ingår i: Genome Research. - : Cold Spring Harbor Laboratory. - 1088-9051 .- 1549-5469. ; 14:10B, s. 2176-2189
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Tidskriftsartikel (refereegranskat)abstract
- Microarray transcript profiling and RNA interference are two new technologies crucial for large-scale gene function studies in multicellular eukaryotes. Both rely on sequence-specific hybridization between complementary nucleic acid strands, inciting us to create a collection of gene-specific sequence tags (GSTs) representing at least 21,500 Arabidopsis genes and which are compatible with both approaches. The GSTs were carefully selected to ensure that each of them shared no significant similarity with any other region in the Arabidopsis genome. They were synthesized by PCR amplification from genomic DNA. Spotted microarrays fabricated from the GSTs show good dynamic range, specificity, and sensitivity in transcript profiling experiments. The GSTs have also been transferred to bacterial plasmid vectors via recombinational cloning protocols. These cloned GSTs constitute the ideal starting point for a variety of functional approaches, including reverse genetics. We have subcloned GSTs on a large scale into vectors designed for gene silencing in plant cells. We show that in planta expression of GST hairpin RNA results in the expected phenotypes in silenced Arabidopsis lines. These versatile GST resources provide novel and powerful tools for functional genomics.
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- Jones, Dylan T, et al.
(författare)
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Albumin activates the AKT signaling pathway and protects B-chronic lymphocytic leukemia cells from chlorambucil- and radiation-induced apoptosis.
- 2003
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 101:8, s. 3174-80
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Tidskriftsartikel (refereegranskat)abstract
- Activation of the phosphatidylinositol 3- kinase/AKT pathway antagonizes apoptosis in diverse cellular systems. We previously showed that human plasma activated AKT and potently blocked the ability of chlorambucil or gamma radiation to induce apoptosis of B-chronic lymphocytic leukemia (CLL) cells. Here we report experiments that identify albumin as the major component of plasma that blocks CLL cell killing by chlorambucil or radiation. Intact plasma depleted of albumin by chromatography on Cibacron blue-Sepharose or plasma from a subject with analbuminemia failed either to activate AKT or to protect CLL cells from chlorambucil-induced apoptosis. Both functions were restored by re-addition of albumin. The protective action of albumin as well as AKT activation was compromised by the binding of lipids. Fluorescence-activated cell sorter (FACScan) analysis demonstrated the uptake of fluoresceinated albumin by CLL cells. Accumulation of albumin in intracellular vesicles was also shown by confocal microscopy. Indirect inhibition of AKT activation by the phosphatidylinositol 3-kinase inhibitor LY294002 reversed the blockade of chlorambucil-induced killing by plasma albumin. The data suggest that activation of AKT consequent to binding of albumin by CLL cells blocks chlorambucil- and radiation-induced apoptosis. Strategies designed to block albumin-induced antiapoptotic signaling may, therefore, be of value in enhancing cytotoxic drug action on CLL cells.
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- Wu, Alan H B, et al.
(författare)
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Analytical and clinical evaluation of the Bayer ADVIA Centaur automated B-type natriuretic peptide assay in patients with heart failure : a multisite study
- 2004
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 50:5, s. 867-873
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:B-Type natriuretic peptide (BNP) is released from the left ventricle of the heart into the circulation in response to ventricular stretching and volume overload. Increased BNP concentrations are associated with heart failure (HF).METHODS:We evaluated the analytical and clinical performance of the Bayer ADVIA Centaur BNP assay. Studies included precision, analytical correlation (against the Shionogi ShionoRIA and Biosite Triage BNP assays), BNP results for blood collected in plastic tubes containing EDTA vs other collection tubes, high-dose hook effect, detection limits, and interferences. The clinical performance was tested on 2243 blood samples collected from 983 apparently healthy individuals, 538 patients with chronic disease but without HF (renal insufficiency, chronic obstructive pulmonary disease, diabetes, and hypertension), and 722 patients with HF (New York Heart Association classes I-IV).RESULTS:The ADVIA Centaur assay had total imprecision (CV) of 3.4%, 2.9%, and 2.4% at BNP concentrations of 48, 461, and 1768 ng/L, respectively. The Passing-Bablok correlations to the ShionoRIA and Triage were as follows: ADVIA Centaur = 1.11(ShionoRIA) - 1.19 ng/L (r = 0.98); ADVIA Centaur = 0.78(Triage) + 5.89 ng/L (r = 0.92), respectively. Of the different blood collection tubes, only EDTA plastic tubes (with and without the barrier gel) were acceptable. The lower detection limit was 0.5 ng/L, and there were no interferences from common analytes, other neuropeptides, or unusual antibodies. BNP exhibited different reference intervals according to age and gender. BNP concentrations increased progressively as the severity of HF increased.CONCLUSIONS:The ADVIA Centaur is the first commercially available BNP assay for use on an automated immunochemistry platform. This assay has good analytical and clinical performance characteristics for diagnosing HF.
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