Specificity of Bacillus thuringiensis delta-endotoxins is correlated with the presence of high-affinity binding sites in the brush border membrane of target insect midguts
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The correlation between toxicity and specific binding is further strengthened by competition studies, as toxins active against dipteran or coleopteran larvae do not compete, and B. thuringiensis delta-endotoxins active against M. sexta compete for binding of 125I-labeled Bt2-toxin to M. brassicae vesicles.Abstract:
Binding studies were performed with two 125I-labeled Bacillus thuringiensis delta-endotoxins on brush border membrane vesicles prepared from the larval midgut of the tobacco hornworm Manduca sexta or the cabbage butterfly Pieris brassicae. One delta-endotoxin, Bt2-protoxin, is a 130-kDa recombinant crystalline protein from B. thuringiensis subsp. berliner. It kills larvae of both insect species. The active Bt2-toxin is a 60-kDa proteolytic fragment of the Bt2-protoxin. It binds saturably and with high affinity to brush border membrane vesicles from the midgut of both species. The other delta-endotoxin, Bt4412-protoxin, is a 136-kDa crystalline protein from B. thuringiensis subsp. thuringiensis, which is highly toxic for P. brassicae, but not for M. sexta larvae. Bt4412-toxin, obtained after proteolytic activation of Bt4412-protoxin, shows high-affinity saturable binding to P. brassicae vesicles but not to M. sexta vesicles. The correlation between toxicity and specific binding is further strengthened by competition studies. Other B. thuringiensis delta-endotoxins active against M. sexta compete for binding of 125I-labeled Bt2-toxin to M. sexta vesicles, whereas toxins active against dipteran or coleopteran larvae do not compete. Bt2-toxin and Bt4412-toxin bind to different sites on P. brassicae vesicles.read more
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Journal ArticleDOI
Bacillus thuringiensis and Its Pesticidal Crystal Proteins
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TL;DR: Researchers are reporting promising results in engineering more-useful toxins and formulations, in creating transgenic plants that express pesticidal activity, and in constructing integrated management strategies to insure that these products are utilized with maximum efficiency and benefit.
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Insecticidal crystal proteins of Bacillus thuringiensis.
Herman Höfte,H R Whiteley +1 more
TL;DR: In this article, a classification for crystal protein genes of Bacillus thuringiensis is presented, based on the insecticidal spectra and the amino acid sequences of the encoded proteins.
Insecticidal crystal proteins of Bacilllus thuringiensis
H. Höfte,H.R. Whiteley +1 more
TL;DR: Studies on the biochemical mechanisms of toxicity suggest that B. thuringiensis crystal proteins induce the formation of pores in membranes of susceptible cells, and these approaches are potentially powerful strategies for the protection of agriculturally important crops against insect damage.
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Insect Pathogens as Biological Control Agents: Do They Have a Future?
TL;DR: Embedded entomopathogenic viruses, bacteria, fungi, nematodes, and protozoa as inundatively applied microbial control agents can be effective and serve as alternatives to broad-spectrum chemical insecticides.
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Crystal structure of insecticidal delta-endotoxin from Bacillus thuringiensis at 2.5 A resolution.
TL;DR: The structure of the δ-endotoxin from Bacillus thuringiensis subsp.
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