Partial purification of Cry 1A toxin-binding proteins from Helicoverpa armigera larval midgut |
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Authors: | Bagchi T |
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Institution: | (1) Department of Microbiology and Biotechnology Centre, Faculty of Science, M.S. University, Baroda, India, 390002 |
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Abstract: | Toxicity of insecticidal endotoxins produced by Bacillus thuringiensis correlates with the presence of specific proteins in the midgut of susceptible larvae. This study was aimed at identifying
and purifying Cry 1A binding proteins from Helicoverpa armigera, an important crop pest of India. B. thuringiensis strain HD 73 which produces Cry 1Ac toxin, specific for H. armigera was used in this study. Toxin-binding proteins from insect larvae were detected by employing a toxin overlay assay using
both radiolabelled as well as unlabelled toxin. Detergent-solubilized fractions of larval brush border membranes were subjected
to soybean agglutinin (SBA) chromatography, from which N-acetylgalactosamine (NAG)-containing proteins were eluted. Analysis of the SBA-purified proteins indicated that four proteins
of approximately 97, 120, 170 and 200 kDa could bind to Cry 1Ac toxin, and three proteins of 97, 170 and 200 kDa proteins
could bind to Cry 1Ab. Furthermore, in the presence of excess Cry 1Ab toxin, the labelled Cry 1Ac toxin could bind only to
170 and 200 kDa proteins, implying that Cry 1Ab can also bind the 120 kDa protein. This study therefore demonstrates that
in H. armigera, midgut proteins of 97, 120, 170 and 200 kDa have the ability to bind both Cry 1Ab and Cry 1Ac. Furthermore, while the 170
and 200 kDa proteins have higher affinity for Cry 1Ac, the 97 kDa has higher affinity for Cry1 Ab.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Bacillus thuringiensis Cry 1Ab binding proteins Cry 1Ab toxin Cry 1Ac binding proteins Cry 1Ac toxin Helicoverpa armigera soybean agglutinin affinity chromatography |
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