Specificity of Insecticidal Crystal Proteins

Milne, Robert W.; Ge, Anni; Rivers, David S.; Dean, Donald H.

doi:10.1021/bk-1990-0432.ch004

Cited by 6 publications

(5 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The mutant protoxins were analyzed by B. mori bioassay (Table I). The control P4102 (CrylAa protoxin) LC50 values were similar to those in published reports (Ge et al, 1989;Milne et al, 1990). P4111 shows a 6-fold reduction in B. mori toxicity when compared to P4102.…”

Section: Resultssupporting

confidence: 85%

“…The other three mutant protoxins, P4III/G43SQ, P4III/AF439, and P4III/S446Y, Table II contains the results of the M. sexta bioassay. P4102 and P4202 demonstrate insecticidal activity in the range of published results (Schnepf et al, 1990;Milne et al, 1990). P4111 possesses close to a three-fold reduction in activity.…”

Section: Resultsmentioning

confidence: 62%

“…P4211, also, demonstrated a large decrease in B. mori insecticidal activity when compared to P4202 (CrylAc), a decrease of at least 17-fold (Lee et al, 1991). In H. virescens bioassays, P4111 demonstrated at least a 2.2-fold decrease in toxicity and P4211 was shown to have a similar reduction in activity of 2.6-fold (Ge et al, 1990). The reduction in the H. virescens activity of both chimeric proteins is interesting in that the H. virescens specificity determining region is located outside of the Clal-Sacl region of the CrylAc toxin.…”

mentioning

confidence: 91%

See 2 more Smart Citations

Suppression of protein structure destabilizing mutations in Bacillus thuringiensis .delta.-endotoxins by second site mutations

Almond¹,

Dean²

1993

Biochemistry

View full text Add to dashboard Cite

Reciprocal exchange of a small region (residues 428-450) within the specificity determining region of two Bacillus thuringiensis delta-endotoxins, CryIAa and CryIAc, resulted in two recombinant proteins that possess a decreased insecticidal activity to Bombyx mori and Manduca sexta. Site-directed mutations introduced in this region of one of the recombinant proteins, with the intent of restoring insecticidal activity, resulted in further reduction of toxicity. We determined that the loss of insecticidal activity in the mutants and the original recombinants was associated with altered toxin protein structure, as measured by sensitivity to intracellular and exogenous proteases. The structural instability of the site-directed mutant proteins could be suppressed genetically by subcloning the mutated region into cryIAc or by introducing second site mutations in defined regions of the mutated cryIAa gene. The second site mutations, by themselves, also produced unstable proteins. In the course of this study, we demonstrated that this small region does not suffice as a specificity determining region for M. sexta.

show abstract

Section: Resultssupporting

confidence: 85%

Section: Resultsmentioning

confidence: 62%

mentioning

confidence: 91%

See 1 more Smart Citation

Suppression of protein structure destabilizing mutations in Bacillus thuringiensis .delta.-endotoxins by second site mutations

Almond¹,

Dean²

1993

Biochemistry

View full text Add to dashboard Cite

show abstract

“…kurstaki contains genes for different insecticidal crystal proteins: CryIAa, CryIAb, CryIAc, CryIIA, and CryIIB. Although the CryIA-type proteins share about 90% amino acid sequence identity, different insecticidal specificities have been reported for several lepidopteran insects (3,4,13).…”

mentioning

confidence: 99%

Synergistic effect of the Bacillus thuringiensis toxins CryIAa and CryIAc on the gypsy moth, Lymantria dispar

Lee

Curtiss

Alcantara

et al. 1996

Appl Environ Microbiol

View full text Add to dashboard Cite

The insecticidal activity of toxins CryIAa, CryIAb, and CryIAc against Lymantria dispar (gypsy moth) and Bombyx mori (silkworm) was examined by force-feeding bioassays. Toxin CryIAa exhibited higher toxicity than toxins CryIAb and CryIAc for L. dispar and B. mori. To evaluate possible synergism among these toxins, bioassays were performed with mixtures of CryIAa and CryIAb, CryIAb and CryIAc, and CryIAa and CryIAc. Expected toxicity was calculated from the activity of each individual toxin and its proportion in the mixture by using the equation described by Tabashnik (B. E. Tabashnik, Appl. Environ. Microbiol. 58:3343-3346, 1992). Observed 50% growth-inhibitory doses were calculated from mixing experiments by probit analysis. In L. dispar bioassays, synergism was observed with a mixture of CryIAa and CryIAc while a mixture of CryIAa and CryIAb exhibited an antagonistic effect. No synergistic effect on B. mori was observed with any toxin combination. Voltage clamping assays of isolated L. dispar midguts also demonstrated that the mixture of CryIAa and CryIAc induced a greater slope of inhibition of short circuit current than did other toxin combinations.

show abstract

“…kurstaki HD-1, contains genes that code for at least five insecticidal crystal proteins: CryIA(a), CryIA(b), CryIA(c), CryIIA, and CryIIB (8). The relative toxicities of individual CrylA proteins from HD-1, which have been reported for at least 18 different species of Lepidoptera, vary widely among species (8,11,14,15,22). These differences in specificity, which occur despite 82 to 90% amino acid identity between pairs of CryIA proteins (8), indicate functional differences among toxins.…”

mentioning

confidence: 99%

Evaluation of synergism among Bacillus thuringiensis toxins

Tabashnik

1992

Appl Environ Microbiol

199

114

View full text Add to dashboard Cite

A simple test for synergism among toxins is described and applied to previously reported data on independent and joint toxicities of insecticidal proteins from BaciUus thuringiensis. The analysis shows synergism between a 27-kDa (CytA) toxin and 130or 65-kDa (CryIV) toxins from B. thuringiensis subsp. israelensis against Aedes aegypti larvae. No positive synergism between 130and 65-kDa toxins or among three CrylA toxins tested against seven species of Lepidoptera occurred. Comparisons with the original interpretations of these data show one case in which synergism occurred but was reported previously as absent and two cases that were not synergistic but were reported previously as suggestive of synergism. These results show that lack of an appropriate test for synergism can produce misleading conclusions. The methods described here can be used to test for synergistic effects of any poisons.

show abstract

Specificity of Insecticidal Crystal Proteins

Cited by 6 publications

References 0 publications

Suppression of protein structure destabilizing mutations in Bacillus thuringiensis .delta.-endotoxins by second site mutations

Suppression of protein structure destabilizing mutations in Bacillus thuringiensis .delta.-endotoxins by second site mutations

Synergistic effect of the Bacillus thuringiensis toxins CryIAa and CryIAc on the gypsy moth, Lymantria dispar

Evaluation of synergism among Bacillus thuringiensis toxins

Contact Info

Product

Resources

About