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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 1 (1987), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: An insecticidal protein gene from Bacillus thuringiensis var. aizawal was cloned in Escherichia coli. The cloned gene expressed at a high level and the synthesized protein appeared as an insoluble, phase-bright inclusion in the cytoplasm. These inclusions were isolated by density gradient centrifugation, the isolated protein was activated in vitro by different proteloytic regimes and the toxicity of the resulting preparations was studied using insect cells grown in tissue culture. The inclusions consisted of a 130 kDa polypeptide which was processed to a protease-resist-ant 55 kDa protein by tryptic digestion. This preparation lysed lepidopteran (Choristoneura fumiferana) CFI ceils but not dipteran (Aedes albopictus) calls. When the crystal protein was activated by sequential treatment, first with trypsin and then with Aedes aegypti gut proteases, the resulting 53 kDa polypeptide was now toxic only to the dipteran cells and not to the lepidopteran cells. Thus the dual specificity of this var. aizawal toxin results from differential proteolytic processing of a single protoxin. The trypsin-activated preparation was weakly active against Spodoptera frugiperda cells. Membrane binding studies of the trypsin-activated toxin revealed a 68 kDa protein in the lepidopteran ceil membranes, which may be the receptor for this toxin.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 2 (1988), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Bacillus thuringlensis var. aizawai HD–249 produces more than one protein of 130–135 kD in its insecticidal crystal δ-endotoxin. We describe an indirect method of assessing the relative contribution to toxicity of two of these protoxins using monospecific antibodies directed against their active proteolytic products. Our results show that one toxin is active against Spodoptera frugiperda but not Choristoneura fumiferana cells in vitro, while the other lyses C. fumiferana but not S. frugiperda cells. There is no indication of synergism between these toxins in vitro.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The hypothesis tested was that a particular glycoconjugate(s) in the exposed cell-surface membrane of susceptible insect cells acts as a receptor and/or modulator for the specific interaction with the protoxin/activated toxin of the δ-endotoxin of Bacillus thuringiensis var. kurstaki. As candidates, the total neutral and acidic fraction glycolipids, and the isolated neutral glycosphingolipid components, were screened for binding activity by the thin layer chromatogram overlay technique. The main protoxin/activated toxin-binding glycolipid in the neutral fraction (5B) had the structure: Gal(α1-3)GalNAc(β1-4)GlcNAc(β1-3)Man(β1-4)Glc(β1-1)Cer. The main protoxin/activated toxin-binding glycolipid in the acidic fraction was designated band 1, the structure of which is at present unknown. The possibility that the component 5B carbohydrate sequence may also function as a toxin-binding site of relevant insect plasma membrane glycoproteins is discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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