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Title: Single-reversal charge in the β10-β11 receptor-binding loop of Bacillus thuringiensis Cry4Aa and Cry4Ba toxins reflects their different toxicity against Culex spp. larvae
Authors: Sarinporn Visitsattapongse
Somsri Sakdee
Somphob Leetacheewa
Chanan Angsuthanasombat
Mahidol University
Biophysics Institute for Research and Development (BIRD)
Keywords: Biochemistry, Genetics and Molecular Biology
Issue Date: 25-Jul-2014
Citation: Biochemical and Biophysical Research Communications. Vol.450, No.2 (2014), 948-952
Abstract: Bacillus thuringiensis Cry4Aa toxin was previously shown to be much more toxic to Culex mosquito-larvae than its closely related toxin - Cry4Ba, conceivably due to their sequence differences within the β10-β11 receptor-binding loop. Here, single-Ala substitutions of five residues (Pro510, Thr512, Tyr513, Lys514and Thr515) within the Cry4Aa β10-β11 loop revealed that only Lys514corresponding to the relative position of Cry4Ba-Asp454is crucial for toxicity against Culex quinquefasciatus larvae. Interestingly, charge-reversal mutations at Cry4Ba-Asp454(D454R and D454K) revealed a marked increase in toxicity against such less-susceptible larvae. In situ binding analyses revealed that both Cry4Ba-D454R and D454K mutants exhibited a significant increase in binding to apical microvilli of Culex larval midguts, albeit at lower-binding activity when compared with Cry4Aa. Altogether, our present data suggest that a positively charged side-chain near the tip of the β10-β11 loop plays a critical role in determining target specificity of Cry4Aa against Culex spp., and hence a great increase in the Culex larval toxicity of Cry4Ba was obtained toward an opposite-charge conversion of the corresponding Asp454. © 2014 Elsevier Inc. All rights reserved.
ISSN: 10902104
Appears in Collections:Scopus 2011-2015

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