BACILLUS-THURINGIENSIS DELTA-ENDOTOXIN AND LARVAL MANDUCA-SEXTA MIDGUT BRUSH-BORDER MEMBRANE-VESICLES ACT SYNERGISTICALLY TO CAUSE VERY LARGE INCREASES IN THE CONDUCTANCE OF PLANAR LIPID BILAYERS

Brush-border membrane vesicles prepared from midguts of Manduca sexta larvae were incorporated into planar phospholipid bilayers. Addition of Bacillus thuringiensis delta-endotoxin to the buffered salt solutions bathing these bilayers resulted in large irreversible increases in conductance. At pH 9.6, the smallest toxin-dependent increase in bilayer conductance observed was 13 nS. Similar conductance increases were never observed in the absence of delta-endotoxin or in delta-endotoxin-treated bilayers not containing components of insect brush-border membranes.