Delta endotoxin inhibits Rb+ uptake, lowers cytoplasmic pH and inhibits a K+-ATPase inManduca sexta CHE cells

Abstract
Summary Delta endotoxin, a 68 kilodalton protein isolated fromBacillus thuringiensis spp.Kurstaki, is a potent entomocidal agent that alters a K+ current across midgut tissue of many phytophagous insects. This toxin completely inhibited the vanadate-sensitive86Rb+ uptake and mimicked the vanadate-induced decrease in cytosolic pH in a cell line (CHE) originating fromManduca sexta embryonic tissue. The toxin also inhibited a K+-sensitive-ATPase in the plasma membranes isolated from these cells. Using the K+-sensitive-ATPase substratp-nitrophenyl phosphate, delta endotoxin was found to have aK i of 0.4 μm. These data suggest that the toxin inhibits a K+-ATPase responsible for86Pb+ uptake in the CHE cells. The relationship between the toxin inhibition of K+-ATPase and toxin-altered K+ current is discussed.

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