In vivo binding of the Cry11Bb toxin of Bacillus thuringiensis subsp. medellin to the midgut of mosquito larvae (Diptera: Culicidae)

Ruíz, Lina; Segura, Cesar; Trujillo, Judith; Ordúz, Sergio

doi:10.1590/s0074-02762004000100013

Cited by 57 publications

(37 citation statements)

References 30 publications

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“…medellin as a 94-kDa protein composed of 782 amino acid residues (56), and its three-dimensional structure with nine ␣ helixes in the domain I has been proposed earlier (57). This protein is toxic for mosquito larvae (44, 56) after activation by mosquito larvae midgut proteases (58) and further membrane binding and permeabilization of the midgut epithelial cells (59). It has not been clear up to now which are the smallest fragments of the Cry11Bb protoxin that can permeabilize biomembranes, although Segura et al (58) proposed that the 94-kDa protoxin is activated to form 30-and 35-kDa fragments.…”

Section: Discussionmentioning

confidence: 99%

Mitochondria Permeabilization by a Novel Polycation Peptide BTM-P1

Lemeshko

Arias

Ordúz

2005

Journal of Biological Chemistry

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Bacillus thuringiensis subsp. medellin is known to produce the Cry11Bb protein of 94 kDa, which is toxic for mosquito larvae due to permeabilization of the plasma membrane of midgut epithelial cells. Earlier we found that a 2.8-kDa novel peptide BTM-P1, which was artificially synthesized taking into account the primary structure of Cry11Bb endotoxin, is active against several species of bacteria. In this work we show that BTM-P1 induces cyclosporin A-insensitive swelling of rat liver mitochondria in various salt solutions but not in the sucrose medium. Inorganic phosphate and Ca 2؉ significantly increased this effect of the peptide. The uncoupling action of BTM-P1 on oxidative phosphorylation was stronger in the potassiumcontaining media and correlated with a decrease of the inner membrane potential of mitochondria. In isotonic KNO 3 , KCl, or NH 4 NO 3 media, a complete drop of the inner membrane potential was observed at 1-2 g/ml of the peptide. The peptide-induced swelling was increased by energization of mitochondria in the potassium-containing media, but it was inhibited in the NaNO 3 , NH 4 NO 3 , and Tris-NO 3 media. All mitochondrial effects of the peptide were completely prevented by adding a single N-terminal tryptophan residue to the peptide sequence. We suggest a mechanism of membrane permeabilization that includes a transmembrane-and surface potential-dependent insertion of the polycation peptide into the lipid bilayer and its oligomerization leading to formation of ion channels and also to the mitochondrial permeability transition pore opening in a cyclosporin A-insensitive manner.

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Section: Discussionmentioning

confidence: 99%

Mitochondria Permeabilization by a Novel Polycation Peptide BTM-P1

Lemeshko

Arias

Ordúz

2005

Journal of Biological Chemistry

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“…Five micron sections were obtained and placed in carriers loaded with a mix of 1.5% egg albumin and 3% glycerol in distilled water. For the investigation of the BNS3 histopathological localization, the 5 lm sections already de-paraffinated in 100% toluene were stained with hematoxylin-eosin (HE) as reported by Ruiz et al [14].…”

Section: Preparation and Sectioning Of Insect Tissuesmentioning

confidence: 99%

“…Detection of the Cry1Aa or Cry1Ac toxins was performed through modification of the technique developed by Ruiz et al [14]. The sections were de-paraffinated in 100% toluene and hydrated in decreasing concentrations of ethanol, washed in distilled water and stored in Tris buffer saline TBS (66 mM NaCl, 1.6 mM KCl, 25 mM Tris base, pH 7.4, ion counter K + ).…”

Section: Immunohistochemical Localization Of the Toxinsmentioning

confidence: 99%

Comparative Study of Bacillus thuringiensis Cry1Aa and Cry1Ac δ-Endotoxin Activation, Inactivation and In Situ Histopathological Effect in Ephestia kuehniella (Lepidoptera: Pyralidae)

2007

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A comparative study of different steps in the mode of action of the individual Bacillus thuringiensis kurstaki BNS3 Cry1Aa and Cry1Ac delta-endotoxins on E. kuehniella larvae was performed in order to investigate the origin of the difference in the response of this larvae to each of the latter. Proteolytic activation was shown to be one of the main steps impaired in E. kuehniella tolerance to Cry1Aa. The absence of two proteinase activities as well as an altered activity level observed in the case of Cry1Aa would be the consequence of proteinase-mediated tolerance of E. kuehniella to this toxin. In situ binding and histopathological effect analyses allowed concluding that the binding of the toxin to BBMV receptors is the key step in E. kuehniella tolerance to Cry1Aa toxin. The latter was slightly bound to apical membranes of epithelial cells that remained intact, whereas Cry1Ac was tightly bound to completely damaged cells basal membranes.

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“…Upon ingestion by susceptible insects, these crystals are dissolved in the midgut lumen. Under the action of intestinal proteases, the endotoxins are converted into active toxins that bind to receptors present on the microvilli, causing strong damages to the epithelial midgut cells (Gill 1992, Aronson & Shai 2001, Ruiz et al 2004.…”

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confidence: 99%