Subdomain organization ofBacillus thuringiensis entomocidal proteins' N-terminal domains

N-Terminal domain (65 kD) of δ-endotoxin produced byBacillus thuringiensis ssp.alesti, as shown by limited proteolysis, consists of two subdomains of molecular mass 30 and 33 kD that correspond, respectively, to conservative and variable regions of the δ-endotoxin primary structure. Furthermore, proteolysis of these subdomains leads to their conversion into at least two fragments of molecular mass 10 kD stable to proteinase action. Such a pattern of molecular organization appears to be common for several structurally related δ-endotoxins that belong to thekurstaki group. Entomicidal protein produced by ssp.israelensis (70 kD), which differs strongly fromalesti and otherkurstaki group δ-endotoxins, retains a similar type of molecular organization and consists of two subdomains with molecular mass of ～35 kD. Apparently, the characteristic pattern of the δ-endotoxins' molecular structure reflects separation of functions (e.g., host recognition and toxicityper se) between domains and subdomains of these proteins.