Abstract: Toxicity of Bacillus thuringiensis deltaendotoxin is interrelated to larval midgut membrane receptor and its binding affinity and numbers.Binding to a specific receptor is an important determinant with respect to differences in insecticidal spectrum of Bacillus thuringiensis deltaendotoxin.Membrane receptor has different binding sites which can interact specially with different binding determinants on the toxin molecules.Meanwhile,endotoxin might interact with more than one receptor in BBMV.The interaction of toxin and membrane receptor shows both the complexity and diversity,but not only recognizing one by one simply.Insect resistance to Bt is also related to the midgut membrane receptor in binding sites,affinity and numbers.It was shown that midgut membrane receptors are brush border membrane vesicles on the membrane of midgut epithelial cells,they belong to aminopeptidase family or cadherin family.Aminopeptidase acts as receptor just on its presence,but not its enzymatic activity.

Key words: midgut receptor, Bacillus thuringiensis, aminopeptidase, cadherin