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Title: Amino acid residues in the N-terminal region of the BinB subunit of Lysinibacillus sphaericus binary toxin play a critical role during receptor binding and membrane insertion
Authors: Kamonnut Singkhamanan
Boonhiang Promdonkoy
Toemsak Srikhirin
Panadda Boonserm
Mahidol University
Prince of Songkla University
Thailand National Center for Genetic Engineering and Biotechnology
Keywords: Agricultural and Biological Sciences
Issue Date: 1-Sep-2013
Citation: Journal of Invertebrate Pathology. Vol.114, No.1 (2013), 65-70
Abstract: The binary toxin produced by Lysinibacillus sphaericus is composed of BinA and BinB subunits that work together in governing toxicity against mosquito larvae. BinA is proposed to be important for toxicity, whereas BinB has been shown to act as a specific receptor-binding component. The precise function of both subunits, however, is not well established. Here, we investigated the function of the N-terminal region of BinB subunit initially by introducing triple alanine substitutions at positions35PEI37and41FYN43. Both block mutations abolished the larvicidal activity. Single point mutations (P35A, E36A, I37A, F41A, Y42A, N43A) were generated in order to identify amino acids that are critical for the toxin activity. Mosquito-larvicidal activity was significantly reduced in P35A, E36A, F41A and Y42A mutants. However, these mutants retained ability to form in vitro interaction with the BinA counterpart. Immunohistochemistry analysis revealed that P35A, F41A and N43A bind to the larval midgut membrane at comparable levels to that of the wild type BinB. In contrast, greatly reduced binding activity was observed in the Y42A, suggesting an important role of this residue in receptor binding. Alanine substitution at P35 resulted in a marked decrease in membrane penetration, indicating its functional importance for the membrane insertion. These results suggest the important roles of the N-terminal region of BinB in both the receptor recognition and the membrane interaction. © 2013 Elsevier Inc.
ISSN: 10960805
Appears in Collections:Scopus 2011-2015

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