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Delta-endotoxins form cation-selective channels in planar lipid bilayers
S L Slatin1, C K Abrams, L English
1Albert Einstein College of Medicine, Dept. of Physiology and Biophysics, Bronx, NY 10461.
Biochemical and Biophysical Research Communications
|June 15, 1990
Summary
Bacillus thuringiensis toxins CryIA(c) and CryIIIA form ion channels in lipid bilayers. These cation-selective channels suggest a common mechanism for the toxicity of these insecticidal proteins.
Area of Science:
- Biochemistry
- Molecular Biology
- Membrane Biophysics
Background:
- Bacillus thuringiensis (Bt) produces delta-endotoxins, including CryIA(c) and CryIIIA, known for their insecticidal properties.
- The precise mechanism underlying the toxicity of these Bt delta-endotoxins is not fully elucidated.
Purpose of the Study:
- To investigate the ability of CryIA(c) and CryIIIA delta-endotoxins to form ion-conducting channels in planar lipid bilayers.
- To characterize the properties of these channels, including conductance and ion selectivity.
Main Methods:
- Planar lipid bilayer electrophysiology was used to study toxin-membrane interactions.
- Single-channel recordings were performed to analyze conductance states and ion permeability.
Main Results:
- Both CryIA(c) and CryIIIA toxins formed stable, ion-conducting channels in lipid bilayers.
- Channels exhibited multiple conductance states, ranging from 200 pS to 4000 pS (in 300 mM KCl).
- The channels displayed high cation selectivity, with a K+/Cl- permeability ratio of approximately 25 for both toxins.
Conclusions:
- The formation of ion channels by CryIA(c) and CryIIIA toxins provides a potential mechanism for their toxic action on susceptible cells.
- This suggests a conserved channel-forming mechanism across this family of Bacillus thuringiensis delta-endotoxins.