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  • Ethylene binding  (3)
  • Ethylene (binding site)  (2)
  • Cytokinin  (1)
  • 1
    ISSN: 1432-2048
    Keywords: Key words:Arabidopsis (GTP binding) ; Cytokinin ; Ethylene ; Protein Phosphorylation ; GTP-binding proteins (small)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Binding of [α-32P]guanosine 5′-triphosphate ([α-32P]GTP) has been demonstrated in a Triton X-100-solubilised membrane fraction from leaves of Arabidopsis thaliana (L.) Heynh. Binding was stimulated by 1 h pre-treatment of leaves with ethylene and this effect was antagonised by the inclusion of N6-benzyladenine in the medium used for homogenisation. The ethylene-insensitive mutants eti5 and etr showed contrasting responses. In eti5 the constitutive level of GTP binding was higher than in the wild type whereas in etr the level was much lower. Neither ethylene nor cytokinin affected GTP binding in the mutants. The GTP-binding activity was localised in two bands at 22 and 25 kDa, both of which were immunoprecipitated by anti-pan-Ras antibodies, indicating that the activity is due to small GTP-binding proteins. In a similar membrane fraction, ethylene was shown to increase protein phosphorylation and benzyladenine antagonised this effect. In eti5 the constitutive level of protein phosphorylation was higher than in the wild type, but benzyladenine increased activity substantially while ethylene was without effect. In etr, protein phosphorylation was lower than in the wild type, ethylene was without effect, but cytokinin increased activity. A protein of Mr 17 kDa was detected on gels using antibodies to nucleoside diphosphate kinase. Phosphorylation of this protein was upregulated by ethylene but nucleoside diphosphate kinase activity was unaffected. The results are compared with the effect of the two hormones on the senescence of detached leaves and discussed in relation to pathways proposed for ethylene signal transduction.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Ethylene binding ; Hormone binding ; Phaseolus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The preparation is described of a cell-free system from developing cotyledons of Phaseolus vulgaris cv. Canadian Wonder which is capable of binding ethylene. The binding is saturable and the apparent dissociation constant for ethylene is 6.4·10-10 M in solution. The binding site is associated with subcellular particles and treatment with Triton X-100 results in substantial solubilisation of the activity. The kinetics of association and dissociation of the ligand and the binding site are described. The system is heat labile and binding activity is diminished by treatment with some proteolytic enzymes.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2048
    Keywords: Ethylene binding ; Hormone binding ; Phaseolus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Various protein reactive agents such as dithioerythritol, dithiothreitol, mercaptoethanol and p-chloromercuribenzoate inhibit binding of ethylene to cell free preparations of Phaseolus vulgaris L. The effect of the thiols is partially reversed by treatment with diamide; occupation of the binding site by ligand diminishes the inhibition caused by p-chloromercuribenzoate but not that caused by thiols. Growth regulators other than ethylene do not affect binding. Physiologically active structural analogues of ethylene competitively inhibit binding of the growth regulator and their relative effectiveness in the cell free system closely resembles that in developmental processes controlled ethylene.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Planta 183 (1991), S. 209-217 
    ISSN: 1432-2048
    Keywords: Ethylene binding ; Pisum (ethylene binding)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using in-vivo assays at least two classes of ethylene-binding site are shown to exist in pea epicotyls. These classes appear to have identical affinities for ethylene with a KD of 6 · 10−11-8 · 10−11 M; the fast associating class has high and appropriate affinities for physiologically active analogues of ethylene, and CO2 is without effect upon bfinding. Experiments involving suppression of endogenous ethylene production demonstrate that previous work may have underestimated both the amount of binding sites present and the affinity of such sites for ethylene. The apparent inhibition of binding by silver appears to be the consequence of a stimulation of endogenous ethylene production. The possible role of the sites as ethylene receptors is discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Planta 164 (1985), S. 272-277 
    ISSN: 1432-2048
    Keywords: Binding site (ethylene) ; Ethylene (binding site) ; Phaseolus (ethylene binding)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The solubilised ethylene-binding site (EBS) of Phaseolus vulgaris L. cotyledons is an asymmetrical protein with a sedimentation coefficient of 2 S and a Stoke's radius of 6.1 nm (determined by ultracentrifugation on isokinetic gradients and gel-permeation chromatography, respectively). The molecular weight and frictional ratio were calculated as 52 000–60 000 and 2.37–2.48, respectively. The EBS has an isoelectric point at between pH 3–5, determined by isoelectric focussing and exhibits a negative charge at pH 8 during non-denaturing electrophoresis. The electrical charge on the EBS is shielded; the EBS does not bind to anion-exchange media under the experimental conditions reported here, is not precipitated by ammonium sulphate and does not precipitate at its isoelectric pH. The EBS preferentially partitions into detergent phases. The results indicate that the EBS is a hydrophobic protein complexed with detergent in aqueous solution. The techniques used to characterise the EBS also resulted in varying degress of purification.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2048
    Keywords: Binding site (ethylene) ; Ethylene (binding site) ; Phaseolus (ethylene binding)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ethylene-binding site (EBS) from Phaseolus vulgaris cv. Canadian Wonder cotyledons can be solubilised from 96,000 g pelleted material by Triton X-100 or sodium cholate. Extraction of 96,000 g pellets with acetone, butanol or butanol and ether results in a total loss of ethylene-binding activity. Like the membrane-bound form, the solubilised EBS has an apparent KD(liquid) of 10-10 M at a concentration of 32 pmol EBS per gram tissue fresh weight. Propylene and acetylene act as competitive inhibitors, carbon dioxide appears to promote ethylene binding and ethane has no significant effect. The solubilised EBS is completely denatured affect. The solubilised EBS is completely denatured after 10 min at 70°C, by 1 mM mercaptoethanol and 0.1 mM dithiothreitol, but not by trypsin or chymotrypsin. However, solubilisation decreases the rate constant of association from 103 M-1 s-1 to 101–102 M-1 s-1 and hence does not permit experimental determination of the rate constant of dissociation. The pH optimum for ethylene binding is altered from the range pH 7–10 in the membrane-bound form to the pH range 4–7 in the solubilised form. The EBS appears to be a hydrophobic, intergral membrane protein, which requires a hydrophobic environment to retain its activity. Partitioning of the EBS into polymer phases is determined by the detergent used for solubilisation indicating that when solubilised, the EBS forms a complex with detergent molecules.
    Type of Medium: Electronic Resource
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