Bacillus thuringiensis Cry4Ba toxin employs two receptor-binding loops for synergistic interactions with Cyt2Aa2

Lailak, Chitsirin; Khaokhiew, Tararat; Promptmas, Chamras; Promdonkoy, Boonhiang; Pootanakit, Kusol; Angsuthanasombat, Chanan

doi:10.1016/j.bbrc.2013.04.078

Cited by 16 publications

(12 citation statements)

References 18 publications

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“…Site directed mutagenesis of these regions reduced binding affinity among these proteins and correlated with reduced synergism (Pérez et al, 2005;Canton et al, 2011). Recently, it was shown that synergism between Cyt2Aa and Cry4Ba also depends on their interaction through two exposed loop regions of Cry4Ba domain II (Lailak et al, 2013). The binding interaction between Cyt1Aa and Cry11Aa could occur in solution or after insertion into the membrane as shown by co-immunoprecipitation studies and Enzyme-Linked ImmunoSorbent Assay (ELISA) binding assays (Pérez et al, 2005).…”

Section: Discussionmentioning

confidence: 99%

Oligomerization is a key step in Cyt1Aa membrane insertion and toxicity but not necessary to synergize Cry11Aa toxicity in Aedes aegypti larvae

López-Díaz

Cantón

Gill

et al. 2013

Environmental Microbiology

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Summary Bacillus thuringiensis produces insecticidal Cry and Cyt proteins that are toxic to different insect orders. In addition, Cyt toxins also display haemolytic activity. Both toxins are pore-forming proteins that form oligomeric structures that insert into the target membrane to lyse cells. Cyt toxins play an important role in mosquitocidal activity since they synergize Cry toxins and are able to overcome resistance to Cry toxins. Cry and Cyt toxins interact by specific epitopes, and this interaction is important to induce the synergistic activity observed. It was proposed that Cyt toxins do not interact with protein receptors but directly interacting with the specific midgut cell lipids. Here, we analysed if oligomerization and membrane insertion of Cyt1Aa are necessary steps to synergize Cry11Aa toxicity. We characterized Cyt1Aa helix α-C mutants that were affected in oligomerization, in membrane insertion and also in haemolytic and insecticidal activities. However, these mutants were still able to synergize Cry11Aa toxicity indicating these steps are independent events of Cyt1Aa synergistic activity. Furthermore, the data indicate that formation of stable Cyt1Aa-oligomeric structure is a key step for membrane insertion, haemolysis and insecticidal activity.

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Section: Discussionmentioning

confidence: 99%

Oligomerization is a key step in Cyt1Aa membrane insertion and toxicity but not necessary to synergize Cry11Aa toxicity in Aedes aegypti larvae

López-Díaz

Cantón

Gill

et al. 2013

Environmental Microbiology

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“…aegypti [98]. Despite the low toxicities of Cyt1Aa and of Cyt2Aa of Bt kyushuensis against exposed larvae, they are highly synergistic with the Bti Cry toxins and their combinations [20,22,88,89,90,150,151,152,153,154,155,156,157,158,159]. Each functions as a receptor for Cry4Ba, which binds through its domain II loops, explaining the synergy mechanism [155,159].…”

Section: Synergy Between the Toxins And Resistance Of Targetsmentioning

confidence: 99%

Bacillus thuringiensis subsp. israelensis and Its Dipteran-Specific Toxins

Ben‐Dov

2014

Toxins

195

149

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Bacillus thuringiensis subsp. israelensis (Bti) is the first Bacillus thuringiensis to be found and used as an effective biological control agent against larvae of many mosquito and black fly species around the world. Its larvicidal activity resides in four major (of 134, 128, 72 and 27 kDa) and at least two minor (of 78 and 29 kDa) polypeptides encoded respectively by cry4Aa, cry4Ba, cry11Aa, cyt1Aa, cry10Aa and cyt2Ba, all mapped on the 128 kb plasmid known as pBtoxis. These six δ-endotoxins form a complex parasporal crystalline body with remarkably high, specific and different toxicities to Aedes, Culex and Anopheles larvae. Cry toxins are composed of three domains (perforating domain I and receptor binding II and III) and create cation-selective channels, whereas Cyts are composed of one domain that acts as well as a detergent-like membrane perforator. Despite the low toxicities of Cyt1Aa and Cyt2Ba alone against exposed larvae, they are highly synergistic with the Cry toxins and hence their combinations prevent emergence of resistance in the targets. The lack of significant levels of resistance in field mosquito populations treated for decades with Bti-bioinsecticide suggests that this bacterium will be an effective biocontrol agent for years to come.

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“…In our previous studies, the functional importance of both DI and DII of the two closely related mosquito-specific toxins (i.e., Cry4Aa and Cry4Ba) was intensively investigated [12,13,14,15,16,17,18]. Of particular significance, we have disclosed the intrinsic stability toward the Pro-rich cluster (Pro 193 Pro 194 _Pro 196 ) which is present exclusively in the long loop linking two pore-lining helices (α 4 and α 5 ) within Cry4Aa-DI [13].…”

Section: Introductionmentioning

confidence: 99%

The C-Terminal Domain of the Bacillus thuringiensis Cry4Ba Mosquito-Specific Toxin Serves as a Potential Membrane Anchor

Thammasittirong

Imtong

Sriwimol

et al. 2019

Toxins

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Although the C-terminal domain (DIII) of three-domain Cry insecticidal toxins from Bacillus thuringiensis has been implicated in various biological functions, its exact role still remains to be elucidated. Here, the 21-kDa isolated DIII fragment of the 65-kDa Cry4Ba mosquito-specific toxin was analyzed for its binding characteristics toward lipid-bilayer membranes. When the highly-purified Cry4Ba-DIII protein was structurally verified by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, it revealed the presence of a distinct β-sheet structure, corresponding to its structure embodied in the Cry4Ba crystal structure. Binding analysis via surface plasmon resonance (SPR) spectroscopy revealed that the 21-kDa Cry4Ba-DIII truncate displayed tight binding to immobilized liposome membranes in a two-step manner, exhibiting a dissociation rate constant (kd) comparable to the 65-kDa full-length toxin. Also similar to the Cry4Ba full-length toxin, its isolated DIII truncate was able to anchor a part of its molecule into the immobilized membrane as the SPR signal was still detected after prolonged treatment with proteinase K. However, unlike the full-length active toxin, the DIII truncate was unable to induce membrane permeability of calcein-loaded liposomes or ion-channel formation in planar lipid bilayers. Together, our present data have disclosed a pivotal role of C-terminal DIII in serving as a membrane anchor rather than a pore-forming moiety of the Cry4Ba mosquito-active toxin, highlighting its potential mechanistic contribution to the interaction of the full-length toxin with lipid membranes in mediating toxicity.

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Bacillus thuringiensis Cry4Ba toxin employs two receptor-binding loops for synergistic interactions with Cyt2Aa2

Cited by 16 publications

References 18 publications

Oligomerization is a key step in Cyt1Aa membrane insertion and toxicity but not necessary to synergize Cry11Aa toxicity in Aedes aegypti larvae

Oligomerization is a key step in Cyt1Aa membrane insertion and toxicity but not necessary to synergize Cry11Aa toxicity in Aedes aegypti larvae

Bacillus thuringiensis subsp. israelensis and Its Dipteran-Specific Toxins

The C-Terminal Domain of the Bacillus thuringiensis Cry4Ba Mosquito-Specific Toxin Serves as a Potential Membrane Anchor

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