Intramolecular Proteolytic Cleavage ofBacillus thuringiensisCry3A δ-Endotoxin May Facilitate Its Coleopteran Toxicity

Carroll, Joe; Convents, D; Damme, Jozef Van; Boets, Annemie; Rie, Jeroen Van; Ellar, David J.

doi:10.1006/jipa.1997.4656

Cited by 71 publications

(66 citation statements)

References 37 publications

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“…Cry1Ba and the hybrids derived from its domains I and II show processing by trypsin leading to a smaller-than-expected stable toxin. This result is probably due to trypsin cleavage within domain I, between alpha helices 3 and 4, as reported earlier for Cry1B as well as for Cry3A (7). In contrast to its neutral effect on activity of Cry3A against coleopterans (7), trypsinization of Cry1Ba was shown to reduce its activity against lepidopterans (5,14).…”

Section: Discussionsupporting

confidence: 67%

Bacillus thuringiensis Delta-Endotoxin Cry1C Domain III Can Function as a Specificity Determinant for Spodoptera exigua in Different, but Not All, Cry1-Cry1C Hybrids

Maagd¹,

Weemen-Hendriks²,

Stiekema³

et al. 2000

Appl Environ Microbiol

112

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In order to test our hypothesis that Bacillus thuringiensis delta-endotoxin Cry1Ca domain III functions as a determinant of specificity for Spodoptera exigua, regardless of the origins of domains I and II, we have constructed by cloning and in vivo recombination a collection of hybrid proteins containing domains I and II of various Cry1 toxins combined with domain III of Cry1Ca. Cry1Ab, Cry1Ac, Cry1Ba, Cry1Ea, and Cry1Fa all become more active against S. exigua when their domain III is replaced by (part of) that of Cry1Ca. This result shows that domain III of Cry1Ca is an important and versatile determinant of S. exigua specificity. The toxicity of the hybrids varied by a factor of 40, indicating that domain I and/or II modulate the activity as well. Cry1Da-Cry1Ca hybrids were an exception in that they were not significantly active against S. exigua or Manduca sexta, whereas both parental proteins were highly toxic. Incidentally, in a Cry1Ba-Cry1Ca hybrid, Cry1Ca domain III can also strongly increase toxicity for M. sexta.

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Section: Discussionsupporting

confidence: 67%

Bacillus thuringiensis Delta-Endotoxin Cry1C Domain III Can Function as a Specificity Determinant for Spodoptera exigua in Different, but Not All, Cry1-Cry1C Hybrids

Maagd¹,

Weemen-Hendriks²,

Stiekema³

et al. 2000

Appl Environ Microbiol

112

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“…Although previous studies have shown the ability of some Cry3 proteins to bind to BBMV from Coleoptera (23,(38)(39)(40)(41), this is the first time that Cry7 has been included in binding studies. Homologous-competition assays carried out with chymotrypsin-activated Cry3Bb and Cry3Ca proteins demonstrated that the binding of these two proteins to C. puncticollis BBMV is specific.…”

Section: Discussionmentioning

confidence: 89%

“…These differences could be attributed to differences in the experimental conditions used. The occurrence of two fragments after in vitro proteolytic processing was also described for another member of the Cry7 family (Cry7Ab3) and for members of other families, such as Cry1Ab, Cry3Aa, Cry8D, and Cry9Ca (31)(32)(33)(34)(35)(36)(37).…”

Section: Discussionmentioning

confidence: 90%

Shared Binding Sites for the Bacillus thuringiensis Proteins Cry3Bb, Cry3Ca, and Cry7Aa in the African Sweet Potato Pest Cylas puncticollis (Brentidae)

Hernández‐Martínez

Vera-Velasco

Martínez-Solís

et al. 2014

Appl Environ Microbiol

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bBacillus thuringiensis Cry3Bb, Cry3Ca, and Cry7Aa have been reported to be toxic against larvae of the genus Cylas, which are important pests of sweet potato worldwide and particularly in sub-Saharan Africa. However, relatively little is known about the processing and binding interactions of these coleopteran-specific Cry proteins. The aim of the present study was to determine whether Cry3Bb, Cry3Ca, and Cry7Aa proteins have shared binding sites in Cylas puncticollis to orient the pest resistance strategy by genetic transformation. Interestingly, processing of the 129-kDa Cry7Aa protoxin using commercial trypsin or chymotrypsin rendered two fragments of about 70 kDa and 65 kDa. N-terminal sequencing of the trypsin-activated Cry7Aa fragments revealed that processing occurs at Glu 47 for the 70-kDa form or Ile 88 for the 65-kDa form. Homologous binding assays showed specific binding of the two Cry3 proteins and the 65-kDa Cry7Aa fragment to brush border membrane vesicles (BBMV) from C. puncticollis larvae. The 70-kDa fragment did not bind to BBMV. Heterologous-competition assays showed that Cry3Bb, Cry3Ca, and Cry7Aa (65-kDa fragment) competed for the same binding sites. Hence, our results suggest that pest resistance mediated by the alteration of a shared Cry receptor binding site might render all three Cry toxins ineffective.

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“…A reduction in solubility is speculated to be one potential mechanism for insect resistance [68]. Cry3A protein may be necessary for the solubilization of toxins in the midgut of insects [69]. Most recently, two models were proposed for the action of crystal proteins i.e., the sequential binding model and signaling pathway model [70].…”

Section: Mode Of Actionmentioning

confidence: 99%

An Overview on the Crystal Toxins from <i>Bacillus thuringiensis</i>

Jisha¹,

Smitha²,

Benjamin³

2013

AiM

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Strains of Bacillus thuringiensis (Bt) are known to produce crystalline proteins (δ-endotoxins) concomitantly with sporulation during their stationary phase of growth, which are demonstrated as lethal to lepidopeterous, coleopeterous and dipterous insects in addition to mites, nematodes, protozoa and flukes. Upon ingestion, the δ-nascent endotoxin is an inactive protoxin complex of (Cry alone or Cry and Cyt toxins together) high molecular mass, which is cleaved upon ingestion into the active component proteins at the high alkaline environments in the digestive tract of these agricultural pests. Conventionally, Bt-crystals are being produced employing submerged or liquid fermentation techniques in commercial media, but recently many workers have used solid-state fermentation strategy for the enhanced production of Bt-toxin at low cost. Apart from δ-endotoxin, some isolates of Bt produce another class of insecticidal small molecules called β-exotoxin (thuringiensin), which may be harmful to humans. Moreover, resistance to Bt developed in various target pest is yet another concern for Bt-industry. Following a brief introduction, this review addresses various toxins produced by various strains of Bt, Bt production media and media formulations with emphasis to solid-state fermentation, general structure of Cry toxin, its mode of action, target pests, bioassay, resistance to Bt toxins and resistance management. Briefly, this review would provide the readers an overview on the general aspects of Bt toxin, its general structure and mechanism of action.

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Intramolecular Proteolytic Cleavage ofBacillus thuringiensisCry3A δ-Endotoxin May Facilitate Its Coleopteran Toxicity

Cited by 71 publications

References 37 publications

Bacillus thuringiensis Delta-Endotoxin Cry1C Domain III Can Function as a Specificity Determinant for Spodoptera exigua in Different, but Not All, Cry1-Cry1C Hybrids

Bacillus thuringiensis Delta-Endotoxin Cry1C Domain III Can Function as a Specificity Determinant for Spodoptera exigua in Different, but Not All, Cry1-Cry1C Hybrids

Shared Binding Sites for the Bacillus thuringiensis Proteins Cry3Bb, Cry3Ca, and Cry7Aa in the African Sweet Potato Pest Cylas puncticollis (Brentidae)

An Overview on the Crystal Toxins from <i>Bacillus thuringiensis</i>

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Intramolecular Proteolytic Cleavage ofBacillus thuringiensisCry3A δ-Endotoxin May Facilitate Its Coleopteran Toxicity

Cited by 71 publications

References 37 publications

Bacillus thuringiensis Delta-Endotoxin Cry1C Domain III Can Function as a Specificity Determinant for Spodoptera exigua in Different, but Not All, Cry1-Cry1C Hybrids

Bacillus thuringiensis Delta-Endotoxin Cry1C Domain III Can Function as a Specificity Determinant for Spodoptera exigua in Different, but Not All, Cry1-Cry1C Hybrids

Shared Binding Sites for the Bacillus thuringiensis Proteins Cry3Bb, Cry3Ca, and Cry7Aa in the African Sweet Potato Pest Cylas puncticollis (Brentidae)

An Overview on the Crystal Toxins from &lt;i&gt;Bacillus thuringiensis&lt;/i&gt;

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An Overview on the Crystal Toxins from <i>Bacillus thuringiensis</i>