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Effect of insect larval midgut proteases on the activity of Bacillus thuringiensis Cry toxins.
Appl Environ Microbiol. 2007 Oct; 73(19):6208-13.AE

Abstract

To test the possibility that proteolytic cleavage by midgut juice enzymes could enhance or inhibit the activity of Bacillus thuringiensis insecticidal toxins, once activated, the effects of different toxins on the membrane potential of the epithelial cells of isolated Manduca sexta midguts in the presence and absence of midgut juice were measured. While midgut juice had little effect on the activity of Cry1Aa, Cry1Ac, Cry1Ca, Cry1Ea, and R233A, a mutant of Cry1Aa from which one of the four salt bridges linking domains I and II of the toxin was eliminated, it greatly increased the activity of Cry1Ab. In addition, when tested in the presence of a cocktail of protease inhibitors or when boiled, midgut juice retained almost completely its capacity to enhance Cry1Ab activity, suggesting that proteases were not responsible for the stimulation. On the other hand, in the absence of midgut juice, the cocktail of protease inhibitors also enhanced the activity of Cry1Ab, suggesting that proteolytic cleavage by membrane proteases could render the toxin less effective. The lower toxicity of R233A, despite a similar in vitro pore-forming ability, compared with Cry1Aa, cannot be accounted for by an increased susceptibility to midgut proteases. Although these assays were performed under conditions approaching those found in the larval midgut, the depolarizing activities of the toxins correlated only partially with their toxicities.

Authors+Show Affiliations

Groupe d'Etude des Protéines Membranaires, Université de Montréal, P.O. Box 6128, Centre Ville Station, Montreal, Quebec H3C 3J7, Canada.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

17693568

Citation

Fortier, Mélanie, et al. "Effect of Insect Larval Midgut Proteases On the Activity of Bacillus Thuringiensis Cry Toxins." Applied and Environmental Microbiology, vol. 73, no. 19, 2007, pp. 6208-13.
Fortier M, Vachon V, Frutos R, et al. Effect of insect larval midgut proteases on the activity of Bacillus thuringiensis Cry toxins. Appl Environ Microbiol. 2007;73(19):6208-13.
Fortier, M., Vachon, V., Frutos, R., Schwartz, J. L., & Laprade, R. (2007). Effect of insect larval midgut proteases on the activity of Bacillus thuringiensis Cry toxins. Applied and Environmental Microbiology, 73(19), 6208-13.
Fortier M, et al. Effect of Insect Larval Midgut Proteases On the Activity of Bacillus Thuringiensis Cry Toxins. Appl Environ Microbiol. 2007;73(19):6208-13. PubMed PMID: 17693568.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effect of insect larval midgut proteases on the activity of Bacillus thuringiensis Cry toxins. AU - Fortier,Mélanie, AU - Vachon,Vincent, AU - Frutos,Roger, AU - Schwartz,Jean-Louis, AU - Laprade,Raynald, Y1 - 2007/08/10/ PY - 2007/8/19/pubmed PY - 2008/1/23/medline PY - 2007/8/19/entrez SP - 6208 EP - 13 JF - Applied and environmental microbiology JO - Appl Environ Microbiol VL - 73 IS - 19 N2 - To test the possibility that proteolytic cleavage by midgut juice enzymes could enhance or inhibit the activity of Bacillus thuringiensis insecticidal toxins, once activated, the effects of different toxins on the membrane potential of the epithelial cells of isolated Manduca sexta midguts in the presence and absence of midgut juice were measured. While midgut juice had little effect on the activity of Cry1Aa, Cry1Ac, Cry1Ca, Cry1Ea, and R233A, a mutant of Cry1Aa from which one of the four salt bridges linking domains I and II of the toxin was eliminated, it greatly increased the activity of Cry1Ab. In addition, when tested in the presence of a cocktail of protease inhibitors or when boiled, midgut juice retained almost completely its capacity to enhance Cry1Ab activity, suggesting that proteases were not responsible for the stimulation. On the other hand, in the absence of midgut juice, the cocktail of protease inhibitors also enhanced the activity of Cry1Ab, suggesting that proteolytic cleavage by membrane proteases could render the toxin less effective. The lower toxicity of R233A, despite a similar in vitro pore-forming ability, compared with Cry1Aa, cannot be accounted for by an increased susceptibility to midgut proteases. Although these assays were performed under conditions approaching those found in the larval midgut, the depolarizing activities of the toxins correlated only partially with their toxicities. SN - 0099-2240 UR - https://www.unboundmedicine.com/medline/citation/17693568/Effect_of_insect_larval_midgut_proteases_on_the_activity_of_Bacillus_thuringiensis_Cry_toxins_ L2 - http://aem.asm.org/cgi/pmidlookup?view=long&pmid=17693568 DB - PRIME DP - Unbound Medicine ER -