Cytolytic toxin Cyt1A and its mechanism of membrane damage: data and hypotheses

The Cyt proteins produced by Bacillus thuringiensis var. israelensis and a few other subspecies are toxic in vivo to the larvae of members of the order Diptera, and the proteins show no amino-acid sequence homology to members of the Cry family of delta -endotoxins. The structure of Cyt1A is described, and lipid-induced inhibition of toxicity is outlined, along with the mechanism of membrane damage. A hypothesis of a detergent-like action of Cyt1A is considered, together with suggestions for its experimental testing.