Structural and functional analysis of a cloned delta endotoxin of Bacillus thuringiensis berliner 1715

A plasmid‐encoded crystal protein gene (bt2) has been cloned from Bacillus thuringiensis berliner 1715. In Escherichia coli, it directs the synthesis of the 130‐kDa protein (Bt2) which is toxic to larvae of Pieris brassicae and Manduca sexta. Comparison of the deduced amino acid sequence of this Bt2 protein with the B. thuringiensis kurstaki HD1 Dipel, B. thuringiensis kurstaki HD73 and B. thuringiensis sotto crystal protein sequences suggests that homologous recombination between the different genes has occurred during evolution. Treatment of the Bt2 protein with trypsin or chymotrypsin yields a 60‐kDa protease‐resistant and fully toxic polypeptide. The minimal portion of the Bt2 protein required for toxicity has been determined by analysing the polypeptides produced by deletion derivatives of the bt2 gene. It coincides with the 60‐kDa protease‐resistant Bt2 fragment and it starts between amino acids 29 and 35 at the N‐terminus and terminates between positions 599 and 607 at the C‐terminus.