Mode of Action of δ-Endotoxin from Bacillus thuringiensis var. aizawai

Abstract

CryIA(a) and CryIA(b), δ-Endotoxins from Bacillus thuringiensis var. aizawai, were found to interact with a brush border membrane vesicle (BBMV) prepared from silkworm, Bombyx mori L. The irreversibly bound toxin was resistant to proteinase K, suggesting that it was inserted into lipid bilayer of BBMV. Cultured cabbage looper TN-368 cells swelled during treatment with δ-endotoxin. The cell swelling induced by the toxin was selectively caused with monovalent cations. Effects of pyrethroids on the toxin-induced cell swelling and the effect of various drugs that affect the Na+ or K+ channel suggested that the δ-endotoxin stimulated the Na+ channel of the cell in isotonic NaCl solution and also Na+, K+-ATPase in KCl solution. The content of cGMP in the swollen cells did not increase.