Mode of action of delta-endotoxins from Bacillus thuringiensis: A comparison with other bacterial toxins

Delta-endotoxins are a class of insecticidal proteins produced by Bacillus thuringiensis. While there are many steps in the mode of action of these toxins, they ultimately interact with the insect midgut epithelium, binding and opening cation-selective channels. Delta-endotoxins form cation-selective channels in planar lipid bilayers, suggesting that these channels are responsible for toxicity. In order to be toxic, the required interaction of delta-endotoxins with the midgut epithelium must create a collection of physical-chemical events necessary for a tight association with the membrane, intercalation into the membrane, and formation of an open channel. These events are discussed in relation to the mode of action of other bacterial toxins.