Dominant negative phenotype of Bacillus thuringiensis Cry1Ab, Cry11Aa and Cry4Ba mutants suggest hetero-oligomer formation among different Cry toxins.

<h4>Background</h4>Bacillus thuringiensis Cry toxins are used worldwide in the control of different insect pests important in agriculture or in human health. The Cry proteins are pore-forming toxins that affect the midgut cell of target insects. It was shown that non-toxic Cry1Ab helix α...

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Autores principales:	Daniela Carmona, Claudia Rodríguez-Almazán, Carlos Muñoz-Garay, Leivi Portugal, Claudia Pérez, Ruud A de Maagd, Petra Bakker, Mario Soberón, Alejandra Bravo
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2011
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/dea90dcac82b4e3ab9bd44ec8225e4c1
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spelling	oai:doaj.org-article:dea90dcac82b4e3ab9bd44ec8225e4c12021-11-18T06:53:58ZDominant negative phenotype of Bacillus thuringiensis Cry1Ab, Cry11Aa and Cry4Ba mutants suggest hetero-oligomer formation among different Cry toxins.1932-620310.1371/journal.pone.0019952https://doaj.org/article/dea90dcac82b4e3ab9bd44ec8225e4c12011-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/21603577/?tool=EBIhttps://doaj.org/toc/1932-6203<h4>Background</h4>Bacillus thuringiensis Cry toxins are used worldwide in the control of different insect pests important in agriculture or in human health. The Cry proteins are pore-forming toxins that affect the midgut cell of target insects. It was shown that non-toxic Cry1Ab helix α-4 mutants had a dominant negative (DN) phenotype inhibiting the toxicity of wildtype Cry1Ab when used in equimolar or sub-stoichiometric ratios (1∶1, 0.5∶1, mutant∶wt) indicating that oligomer formation is a key step in toxicity of Cry toxins.<h4>Methodology/principal findings</h4>The DN Cry1Ab-D136N/T143D mutant that is able to block toxicity of Cry1Ab toxin, was used to analyze its capacity to block the activity against Manduca sexta larvae of other Cry1 toxins, such as Cry1Aa, Cry1Ac, Cry1Ca, Cry1Da, Cry1Ea and Cry1Fa. Cry1Ab-DN mutant inhibited toxicity of Cry1Aa, Cry1Ac and Cry1Fa. In addition, we isolated mutants in helix α-4 of Cry4Ba and Cry11Aa, and demonstrate that Cry4Ba-E159K and Cry11Aa-V142D are inactive and completely block the toxicity against Aedes aegypti of both wildtype toxins, when used at sub-stoichiometric ratios, confirming a DN phenotype. As controls we analyzed Cry1Ab-R99A or Cry11Aa-E97A mutants that are located in helix α-3 and are affected in toxin oligomerization. These mutants do not show a DN phenotype but were able to block toxicity when used in 10∶1 or 100∶1 ratios (mutant∶wt) probably by competition of binding with toxin receptors.<h4>Conclusions/significance</h4>We show that DN phenotype can be observed among different Cry toxins suggesting that may interact in vivo forming hetero-oligomers. The DN phenotype cannot be observed in mutants affected in oligomerization, suggesting that this step is important to inhibit toxicity of other toxins.Daniela CarmonaClaudia Rodríguez-AlmazánCarlos Muñoz-GarayLeivi PortugalClaudia PérezRuud A de MaagdPetra BakkerMario SoberónAlejandra BravoPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 6, Iss 5, p e19952 (2011)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Daniela Carmona Claudia Rodríguez-Almazán Carlos Muñoz-Garay Leivi Portugal Claudia Pérez Ruud A de Maagd Petra Bakker Mario Soberón Alejandra Bravo Dominant negative phenotype of Bacillus thuringiensis Cry1Ab, Cry11Aa and Cry4Ba mutants suggest hetero-oligomer formation among different Cry toxins.
description	<h4>Background</h4>Bacillus thuringiensis Cry toxins are used worldwide in the control of different insect pests important in agriculture or in human health. The Cry proteins are pore-forming toxins that affect the midgut cell of target insects. It was shown that non-toxic Cry1Ab helix α-4 mutants had a dominant negative (DN) phenotype inhibiting the toxicity of wildtype Cry1Ab when used in equimolar or sub-stoichiometric ratios (1∶1, 0.5∶1, mutant∶wt) indicating that oligomer formation is a key step in toxicity of Cry toxins.<h4>Methodology/principal findings</h4>The DN Cry1Ab-D136N/T143D mutant that is able to block toxicity of Cry1Ab toxin, was used to analyze its capacity to block the activity against Manduca sexta larvae of other Cry1 toxins, such as Cry1Aa, Cry1Ac, Cry1Ca, Cry1Da, Cry1Ea and Cry1Fa. Cry1Ab-DN mutant inhibited toxicity of Cry1Aa, Cry1Ac and Cry1Fa. In addition, we isolated mutants in helix α-4 of Cry4Ba and Cry11Aa, and demonstrate that Cry4Ba-E159K and Cry11Aa-V142D are inactive and completely block the toxicity against Aedes aegypti of both wildtype toxins, when used at sub-stoichiometric ratios, confirming a DN phenotype. As controls we analyzed Cry1Ab-R99A or Cry11Aa-E97A mutants that are located in helix α-3 and are affected in toxin oligomerization. These mutants do not show a DN phenotype but were able to block toxicity when used in 10∶1 or 100∶1 ratios (mutant∶wt) probably by competition of binding with toxin receptors.<h4>Conclusions/significance</h4>We show that DN phenotype can be observed among different Cry toxins suggesting that may interact in vivo forming hetero-oligomers. The DN phenotype cannot be observed in mutants affected in oligomerization, suggesting that this step is important to inhibit toxicity of other toxins.
format	article
author	Daniela Carmona Claudia Rodríguez-Almazán Carlos Muñoz-Garay Leivi Portugal Claudia Pérez Ruud A de Maagd Petra Bakker Mario Soberón Alejandra Bravo
author_facet	Daniela Carmona Claudia Rodríguez-Almazán Carlos Muñoz-Garay Leivi Portugal Claudia Pérez Ruud A de Maagd Petra Bakker Mario Soberón Alejandra Bravo
author_sort	Daniela Carmona
title	Dominant negative phenotype of Bacillus thuringiensis Cry1Ab, Cry11Aa and Cry4Ba mutants suggest hetero-oligomer formation among different Cry toxins.
title_short	Dominant negative phenotype of Bacillus thuringiensis Cry1Ab, Cry11Aa and Cry4Ba mutants suggest hetero-oligomer formation among different Cry toxins.
title_full	Dominant negative phenotype of Bacillus thuringiensis Cry1Ab, Cry11Aa and Cry4Ba mutants suggest hetero-oligomer formation among different Cry toxins.
title_fullStr	Dominant negative phenotype of Bacillus thuringiensis Cry1Ab, Cry11Aa and Cry4Ba mutants suggest hetero-oligomer formation among different Cry toxins.
title_full_unstemmed	Dominant negative phenotype of Bacillus thuringiensis Cry1Ab, Cry11Aa and Cry4Ba mutants suggest hetero-oligomer formation among different Cry toxins.
title_sort	dominant negative phenotype of bacillus thuringiensis cry1ab, cry11aa and cry4ba mutants suggest hetero-oligomer formation among different cry toxins.
publisher	Public Library of Science (PLoS)
publishDate	2011
url	https://doaj.org/article/dea90dcac82b4e3ab9bd44ec8225e4c1
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Dominant negative phenotype of Bacillus thuringiensis Cry1Ab, Cry11Aa and Cry4Ba mutants suggest hetero-oligomer formation among different Cry toxins.

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