Interaction between mosquito-larvicidal Lysinibacillus sphaericus binary toxin components: analysis of complex
Avinash Kale1, Ramesh S Hire, Ashok B Hadapad
1High Pressure & Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
Abstract:
The two components (BinA and BinB) of Lysinibacillus sphaericus binary toxin together are highly toxic to Culex and Anopheles mosquito larvae, and have been employed world-wide to control mosquito borne diseases. Upon binding to the membrane receptor an oligomeric form (BinA2.BinB2) of the binary toxin is expected to play role in pore formation. It is not clear if these two proteins interact in solution as well, in the absence of receptor. The interactions between active forms of BinA and BinB polypeptides were probed in solution using size-exclusion chromatography, pull-down assay, surface plasmon resonance, circular dichroism, and by chemically crosslinking BinA and BinB components. We demonstrate that the two proteins interact weakly with first association and dissociation rate constants of 4.5×10(3) M(-1) s(-1) and 0.8 s(-1), resulting in conformational change, most likely, in toxic BinA protein that could kinetically favor membrane translocation of the active oligomer. The weak interactions between the two toxin components could be stabilized by glutaraldehyde crosslinking. The cross-linked complex, interestingly, showed maximal Culex larvicidal activity (LC50 value of 1.59 ng mL(-1)) reported so far for combination of BinA/BinB components, and thus is an attractive option for development of new bio-pesticides for control of mosquito borne vector diseases.
Insights
Lysinibacillus sphaericus binary toxin components BinA and BinB weakly interact in solution. Crosslinking these proteins enhances their larvicidal activity, offering a promising strategy for mosquito-borne disease control.
Area of Science:
- Biochemistry
- Molecular Biology
- Entomology
Background:
- Lysinibacillus sphaericus binary toxin (BinA and BinB) is crucial for controlling mosquito-borne diseases.
- The oligomeric form (BinA2.BinB2) is implicated in pore formation upon receptor binding.
- The interaction between BinA and BinB in solution, without a receptor, remains unclear.
Purpose of the Study:
- To investigate the interaction between the active BinA and BinB polypeptides in solution.
- To understand how this interaction influences the toxin's activity.
- To explore the potential of cross-linked BinA/BinB complexes as bio-pesticides.
Main Methods:
- Size-exclusion chromatography
- Pull-down assay
- Surface plasmon resonance
- Circular dichroism
- Chemical crosslinking with glutaraldehyde
Main Results:
- BinA and BinB exhibit weak interactions in solution with specific association and dissociation rate constants.
- This interaction induces a conformational change, likely in BinA, potentially aiding membrane translocation.
- Glutaraldehyde crosslinking stabilizes the BinA-BinB complex.
- The cross-linked complex demonstrated maximal Culex larvicidal activity (LC50 = 1.59 ng mL(-1)).
Conclusions:
- BinA and BinB interact weakly in solution, influencing toxin efficacy.
- Stabilizing this interaction via crosslinking significantly enhances larvicidal potency.
- The cross-linked BinA/BinB complex presents a promising avenue for developing novel bio-pesticides against mosquito vectors.
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