Increased toxicity of modified mosquitocidal binary toxins of Bacillus sphaericus expressed in Escherichia coli |
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Authors: | S Ahmad A Selvapandiyan R K Bhatnagar |
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Institution: | (1) International Centre for Genetic Engineering and Biotechnology, P.O. Box 10504, Aruna Asaf Ali Marg, New Delhi 110 067, India Fax: +91 11 6162316, IN |
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Abstract: | The binary mosquitocidal genes of 51-kDa and 42-kDa proteins isolated from Bacillus sphaericus 1593 have been expressed at moderate levels in Escherichia coli employing the pQE expression system. The expressed proteins are readily visible in Coomassie-blue-stained protein gels. The
recombinant E. coli cells expressing toxic proteins were toxic towards Culex larvae. During the assembly of crystals in B. sphaericus, the 42-kDa toxin is first cleaved at the N-terminal end by a specific B. sphaericus protease. To express the toxins in E. coli the B.sphaericus specific protease-recognition site was deleted at the N-terminal end of the 42-kDa toxin, thereby mimicking the structure
of the toxin as present in the crystal. This modification resulted in a twofold increase in the toxicity of the E. coli cells expressing the modified 42-kDa toxin as a constituent of the binary toxin. Our results demonstrate the utility of this
modification for heterologous expression of the binary toxin genes from B. sphaericus.
Received: 18 July 1997 / Received revision: 6 October 1997 / Accepted: 14 October 1997 |
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