Characterization and partial purification of a plasma membrane receptor for Bacillus thuringiensis var. kurstaki lepidopteran-specific delta-endotoxin

The lepidopteran-specific P1 delta-endotoxin of Bacillus thuringiensis var. kurstaki HD-1 was activated in vitro using insect gut proteases and found to be highly specific for the lepidopteran cell line Choristoneura fumiferana CF1 among a wide range of lepidopteran and dipteran cell lines tested. The toxicity of P1 against CF1 cells is inhibited by N-acetylgalactosamine (GalNAc), and the lectins soybean agglutinin (SBA) and wheat-germ agglutinin. Protein blotting was used to identify a glycoprotein of 146 X 10(3) Mr in the plasma membrane of CF1 cells, capable of binding both the toxin and SBA, which is specific for GalNAc. This glycoprotein was labelled using galactose oxidase and sodium boro-[3H]hydride and solubilized in Triton X-100 before partial purification by affinity chromatography on SBA-agarose. We propose that this glycoprotein is a good candidate for the cellular receptor of the lepidopteran-specific P1 delta-endotoxin of B. thuringiensis var. kurstaki HD-1.