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  • 1
    Electronic Resource
    Electronic Resource
    Colicin M is inactivated during import by its immunity protein (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 388-396 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; Colicin M ; Immunity ; Periplasm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Colicin M (Cma) displays a unique activity that interferes with murein and O-antigen biosynthesis through inhibition of lipid-carrier regeneration. Immunity is conferred by a specific immunity protein (Cmi) that inhibits the action of colicin M in the periplasm. The subcellular location of Cmi was determined by constructing hybrid proteins between Cmi and the TEM-β-lactamase (BlaM), which confers resistance to ampicillin only when it is translocated across the cytoplasmic membrane with the aid of Cmi. The smallest Cmi'-BlaM hybrid that conferred resistance to 50 μg/ml ampicillin contained 19 amino acid residues of Cmi; cells expressing Cmi'-BlaM with only five N-terminal Cmi residues were ampicillin sensitive. These results support a model in which the hydrophobic sequence of Cmi comprising residues 3–23 serves to translocate residues 24–117 of Cmi into the periplasm and anchors Cmi to the cytoplasmic membrane. Residues 8–23 are integrated in the cytoplasmic membrane and are not involved in Cma recognition. This model was further tested by replacing residues 1–23 of Cmi by the hydrophobic amino acid sequence 1–42 of the penicillin binding protein 3 (PBP3). In vivo, PBP3'-'Cmi was as active as Cmi, demonstrating that translocation and anchoring of Cmi is not sequence-specific. Substitution of the 23 N-terminal residues of Cmi by the cleavable signal peptide of BlaM resulted in an active BlaM'-'Cmi hybrid protein. The immunity conferred by BlaM'-'Cmi was high, but not as high as that associated with Cmi and PBP3'-'Cmi, demonstrating that soluble Cmi lacking its membrane anchor is still active, but immobilization in the cytoplasmic membrane, the target site of Cma, increases its efficiency. CmiΔ1-23 remained in the cytoplasm and conferred no immunity. We propose that the immunity protein inactivates colicin M in the periplasm before Cma can reach its target in the cytoplasmic membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02172531
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of dietary nicotine on the fall armyworm, Spodoptera frugiperda and its parasitoid, the ichneumonid wasp Hyposoter annulipes (1988)
    Springer
    Entomologia experimentalis et applicata 46 (1988), S. 227-232 
    Details
    ISSN: 1570-7458
    Keywords: tri-trophic level interactions ; nicotine ; alkaloid ; Hyposoter annulipes ; Hymenoptera ; Ichneumonidae ; fall armyworm ; Spodoptera frugiperda ; Lepidoptera ; Noctuidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Des quantités croissantes de nicotine dans l'alimentation ont prolongé la durée du développement des chenilles saines, bien que l'effet ait chuté aux concentrations les plus élevées. Le sexe de la noctuelle n'a pas eu d'effet sur la durée du développement ou l'action de la nicotine. L'influence de la nicotine sur le poids des chrysalides est inhabituel, en ce sens que les chrysalides les plus lourdes ont été obtenues aux concentrations moyennes. Des hypothèses sont proposés sur l'origine de ce phénomène. La mortalité et la durée de développement de H. annulipes ont augmenté et le poids des adultes a diminué quand la concentration de l'aliment de l'hôte en nicotine s'est élevée. L'effet différente de la nicotine sur des générations successives a pu provenir de modifications de la toxicité de la nicotine en fonction de changements dans la qualité de l'aliment. Quoi qu'il en soit, l'augmentation de la concentration de la nicotine dans l'alimentation de l'hôte a eu un effet négatif cohérent sur la valeur adaptative de H. annulipes.
    Notes: Abstract Experiments were conducted to determine the influence of nicotine (at a range of concentrations) in the food of an herbivorous host on the development, size and survival of its parasitoid. Fall armyworms, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) were reared on diets of 0, 0.025, 0.050 and 0.075% nicotine and exposed to parasitism by Hyposoter annulipes (Hymenoptera: Ichneumonidae). As nicotine concentration increased parasitoid mortality and development time increased and adult weight decreased. Development time, pupal weight and survival were recorded for unparasitized armyworms. Unparasitized fall armyworms showed lengthened development and higher mortality but pupal weights were greatest at intermediate nicotine concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00364193
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    Paper (German National Licenses)
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