Lectin‐like binding of Bacillus thuringiensis var, kurstaki lepidopteran‐specific toxin is an initial step in insecticidal action

Abstract

The two δ‐endotoxins comprising the Bacillus thuringiensis var. kurstaki HD1 insecticidal protein crystal were separated. The lepidopteran‐specific protoxin was activated in vitro and its mechanism of action investigated. Toxicity towards Choristoneura fumiferana CF1 cells was specifically inhibited by preincubation of the toxin with N‐acetylgalactosamine and N‐acetylneuraminic acid. The lectins soybean agglutinin and wheat germ agglutinin, which bind N‐acetylgalactosamine, also inhibited toxicity. Since N‐acetylneuraminic acid is not known to occur in insects, these results suggest that the toxin may recognise a specific plasma membrane glycoconjugate receptor with a terminal N‐acetylgalactosamine residue.