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Pakistan Journal of Biological Sciences

Year: 2001  |  Volume: 4  |  Issue: 5  |  Page No.: 569 - 571

Protease Digestion and Role of N-acetyl Galactosamine in the Binding Characteristics of Bacillus thuringiensis Delta-endotoxin ( Cry 1Ac ) to Purified Receptor of Helicoverpa armigera

Kausar Malik and S. Riazuddin

Abstract

Proteins synthesized by the bacterium Bacillus thuringiensis are potent insecticides. When ingested by susceptible larvae they rapidly lyse epithelial cell lining of the midgut. The receptor protein in Helicoverpa armigera midgut appeared as single band on Non-SDS-PAGE but on SDS-PAGE. It resolved as two subunits (120kDa, 70kDa). We observed that the sugar N-acetyl galactosamine (GalNAc) showed no effect on binding of CryIAc toxin to receptor protein or in other words, toxin binding to receptor was not inhibited by GalNAc. This finding suggest that GalNAc might be not a component of a Cry1Ac toxin receptor Proteolysis of receptor proteins with trypsin and gut juice of Helicoverpa armigera showed that ~120Kda was digested while, ~70 kDa was trypsin and gut juice resistant and showed binding to CryIAc in ligand blots Proteolysis of receptor protein with pronase and proteinase-K showed digestion of ~120 kDa , ~70kDa and less than 40 kDa bands were appeared.

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