scholarly journals Role of GPI-Anchored Membrane Receptors in the Mode of Action of Bacillus thuringiensis Cry Toxins

10.5772/30718 ◽  
2012 ◽  
Author(s):  
Fernando Ziga-Navarrete ◽  
Alejandra Bravo ◽  
Mario Sobern ◽  
Isabel Gmez
Keyword(s):  
Bacillus Thuringiensis ◽  
Mode Of Action ◽  
Membrane Receptors ◽  
Cry Toxins

Role of receptor interaction in the mode of action of insecticidal Cry and Cyt toxins produced by Bacillus thuringiensis

Peptides ◽  
2007 ◽  
Vol 28 (1) ◽  
pp. 169-173 ◽  
Author(s):  
I. Gómez ◽  
L. Pardo-López ◽  
C. Muñoz-Garay ◽  
L.E. Fernandez ◽  
C. Pérez ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Mode Of Action ◽  
Receptor Interaction

scholarly journals Employing phage display to study the mode of action of Bacillus thuringiensis Cry toxins

Peptides ◽  
2008 ◽  
Vol 29 (2) ◽  
pp. 324-329 ◽  
Author(s):  
Luisa Elena Fernández ◽  
Isabel Gómez ◽  
Sabino Pacheco ◽  
Iván Arenas ◽  
Sarjeet S. Gilla ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Phage Display ◽  
Mode Of Action ◽  
Cry Toxins

scholarly journals Key Residues of Bacillus Thuringiensis Cry2Ab for Oligomerization and Pore-Formation Activity

2021 ◽  
Author(s):  
Zhi-Zhen Pan ◽  
Lian Xu ◽  
Bo Liu ◽  
Qing-Xi Chen ◽  
Yu-Jing Zhu
Keyword(s):  
Bacillus Thuringiensis ◽  
Insecticidal Activity ◽  
Mode Of Action ◽  
Pore Formation ◽  
Wild Type ◽  
Cry Toxins ◽  
Key Residues ◽  
Domain I ◽  
First Time

Abstract As a pore-forming toxin, oligomerization and pore-formation were both required for the mode of action of Cry toxins. Previous studies revealed that Domain I helices α4-α5 were involved in oligomerization of Cry2Ab, while the active residues in charge of Cry2Ab aggregation remained ambiguous. In present studies, we built 20 Cry2Ab alanine mutants site directed in helices α4-α5 and demonstrated that mutants N151A, T152A, F157A, L183A, L185A and I188A blocked the assembly of 250 kDa oligomers, suggesting that those residues were key residues for Cry2Ab oligomerization. As expected, those variants severely reduced the insecticidal activity against P. xylostella which was similar to our previous reports. Furthermore, we found that the pore-forming activities of non-oligomerization mutants sharply decreased compared to wild-type Cry2Ab. Taken together, our data comprehensively identified key residues for Cry2Ab for the first time and emphasized that oligomerization was closely related to insecticidal activity and pore-forming activity in Cry2Ab.

scholarly journals Role of Receptors in Bacillus thuringiensis Crystal Toxin Activity

2007 ◽  
Vol 71 (2) ◽  
pp. 255-281 ◽  
Author(s):  
Craig R. Pigott ◽  
David J. Ellar
Keyword(s):  
Bacillus Thuringiensis ◽  
Structural Features ◽  
Small Subset ◽  
Cry Toxins ◽  
Toxin Resistance ◽  
Sequence Of Events ◽  
Crystal Toxin

SUMMARY Bacillus thuringiensis produces crystalline protein inclusions with insecticidal or nematocidal properties. These crystal (Cry) proteins determine a particular strain's toxicity profile. Transgenic crops expressing one or more recombinant Cry toxins have become agriculturally important. Individual Cry toxins are usually toxic to only a few species within an order, and receptors on midgut epithelial cells have been shown to be critical determinants of Cry specificity. The best characterized of these receptors have been identified for lepidopterans, and two major receptor classes have emerged: the aminopeptidase N (APN) receptors and the cadherin-like receptors. Currently, 38 different APNs have been reported for 12 different lepidopterans. Each APN belongs to one of five groups that have unique structural features and Cry-binding properties. While 17 different APNs have been reported to bind to Cry toxins, only 2 have been shown to mediate toxin susceptibly in vivo. In contrast, several cadherin-like proteins bind to Cry toxins and confer toxin susceptibility in vitro, and disruption of the cadherin gene has been associated with toxin resistance. Nonetheless, only a small subset of the lepidopteran-specific Cry toxins has been shown to interact with cadherin-like proteins. This review analyzes the interactions between Cry toxins and their receptors, focusing on the identification and validation of receptors, the molecular basis for receptor recognition, the role of the receptor in resistant insects, and proposed models to explain the sequence of events at the cell surface by which receptor binding leads to cell death.

scholarly journals The Cytocidal Spectrum of Bacillus thuringiensis Toxins: From Insects to Human Cancer Cells

Toxins ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 301 ◽  
Author(s):  
Gretel Mendoza-Almanza ◽  
Edgar L. Esparza-Ibarra ◽  
Jorge L. Ayala-Luján ◽  
Marisa Mercado-Reyes ◽  
Susana Godina-González ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Cell Membrane ◽  
Cancer Cells ◽  
Insecticidal Activity ◽  
Human Cancer ◽  
Membrane Receptors ◽  
Specific Cell ◽  
Cry Proteins ◽  
Cry Toxins ◽  
Human Cancer Cells

Bacillus thuringiensis (Bt) is a ubiquitous bacterium in soils, insect cadavers, phylloplane, water, and stored grain, that produces several proteins, each one toxic to different biological targets such as insects, nematodes, mites, protozoa, and mammalian cells. Most Bt toxins identify their particular target through the recognition of specific cell membrane receptors. Cry proteins are the best-known toxins from Bt and a great amount of research has been published. Cry are cytotoxic to insect larvae that affect important crops recognizing specific cell membrane receptors such as cadherin, aminopeptidase-N, and alkaline phosphatase. Furthermore, some Cry toxins such as Cry4A, Cry4B, and Cry11A act synergistically with Cyt toxins against dipteran larvae vectors of human disease. Research developed with Cry proteins revealed that these toxins also could kill human cancer cells through the interaction with specific receptors. Parasporins are a small group of patented toxins that may or may not have insecticidal activity. These proteins could kill a wide variety of mammalian cancer cells by recognizing specific membrane receptors, just like Cry toxins do. Surface layer proteins (SLP), unlike the other proteins produced by Bt, are also produced by most bacteria and archaebacteria. It was recently demonstrated that SLP produced by Bt could interact with membrane receptors of insect and human cancer cells to kill them. Cyt toxins have a structure that is mostly unrelated to Cry toxins; thereby, other mechanisms of action have been reported to them. These toxins affect mainly mosquitoes that are vectors of human diseases like Anopheles spp (malaria), Aedes spp (dengue, zika, and chikungunya), and Culex spp (Nile fever and Rift Valley fever), respectively. In addition to the Cry, Cyt, and parasporins toxins produced during spore formation as inclusion bodies, Bt strains also produce Vip (Vegetative insecticidal toxins) and Sip (Secreted insecticidal proteins) toxins with insecticidal activity during their vegetative growth phase.

scholarly journals Key residues of Bacillus thuringiensis Cry2Ab for oligomerization and pore-formation activity

AMB Express ◽  
2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhi-Zhen Pan ◽  
Lian Xu ◽  
Bo Liu ◽  
Qing-Xi Chen ◽  
Yu-Jing Zhu
Keyword(s):  
Bacillus Thuringiensis ◽  
Insecticidal Activity ◽  
Mode Of Action ◽  
Pore Formation ◽  
Wild Type ◽  
Cry Toxins ◽  
Key Residues ◽  
Domain I

AbstractAs a pore-forming toxin, activation, oligomerization and pore-formation were both required for the mode of action of Cry toxins. Previous results revealed that the helices α4–α5 of Domain I were involved in the oligomerization of Cry2Ab, however, the key residues for Cry2Ab aggregation remained ambiguous. In present studies, we built 20 Cry2Ab alanine mutants site-directed in the helices α4–α5 of Domain I and demonstrated that mutants N151A, T152A, F157A, L183A, L185A and I188A could reduce the assembly of the 250 kDa oligomers, suggesting that these mutation residues might be essential for Cry2Ab oligomerization. As expected, all of these variants showed lower insecticidal activity against P. xylostella. Furthermore, we found that the pore-forming activities of these mutants also decreased when compared to wild-type Cry2Ab. Taken together, our data identified key residues for Cry2Ab oligomerization and emphasized that oligomerization was closely related to the insecticidal activity and pore-forming activity of Cry2Ab.

scholarly journals Role of Tryptophan Residues in Toxicity of Cry1Ab Toxin from Bacillus thuringiensis

2006 ◽  
Vol 72 (1) ◽  
pp. 901-907 ◽  
Author(s):  
Cristopher Padilla ◽  
Liliana Pardo-López ◽  
Gustavo de la Riva ◽  
Isabel Gómez ◽  
Jorge Sánchez ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Insecticidal Activity ◽  
Structural Changes ◽  
Site Directed Mutagenesis ◽  
Crystal Formation ◽  
Cry Toxins ◽  
Tryptophan Residues ◽  
Cry1ab Toxin ◽  
And Function

ABSTRACT Bacillus thuringiensis produces insecticidal proteins (Cry protoxins) during the sporulation phase as parasporal crystals. During intoxication, the Cry protoxins must change from insoluble crystals into membrane-inserted toxins which form ionic pores. The structural changes of Cry toxins during oligomerization and insertion into the membrane are still unknown. The Cry1Ab toxin has nine tryptophan residues; seven are located in domain I, the pore-forming domain, and two are located in domain II, which is involved in receptor recognition. Eight Trp residues are highly conserved within the whole family of three-domain Cry proteins, suggesting an essential role for these residues in the structural folding and function of the toxin. In this work, we analyzed the role of Trp residues in the structure and function of Cry1Ab toxin. We replaced the Trp residues with phenylalanine or cysteine using site-directed mutagenesis. Our results show that W65 and W316 are important for insecticidal activity of the toxin since their replacement by Phe reduced the toxicity against Manduca sexta. The presence of hydrophobic residue is important at positions 117, 219, 226, and 455 since replacement by Cys affected either the crystal formation or the insecticidal activity of the toxin in contrast to replacement by Phe in these positions. Additionally, some mutants in positions 219, 316, and 455 were also affected in binding to brush border membrane vesicles (BBMV). This is the first report that studies the role of Trp residues in the activity of Cry toxins.

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