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Articles by Kausar Malik
Total Records ( 2 ) for Kausar Malik
  Kausar Malik , Tariq Mahmood and S. Riazuddin
  120 Kda and 70 Kda protein in the larval midgut membrane of the lepidopteran Helicoverpa armigera identified as putative receptor for Bt Cry 1Ac delta-endotoxin .Receptor proteins have been purified by a combination of gel-filtration and anion exchange chromatography .In ligand-blotting experiment ,the purified protein has binding capacity with Cry 1Ac and Cry 1Ab but not to Cry 2A .N-terminal sequence obtained from the protein show no homology to already existing sequences .When assayed for amino-peptidase and alkaline phosphatase activities , purified receptors preparations were enriched 2.5 fold in amino-peptidase activity compare to Helicoverpa-armigera brush border membrane vesicles . The 70 Kda protein seems to be the part of 120 Kda receptor protein.
  Kausar Malik and S. Riazuddin
  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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