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journal1 ›› 2018, Vol. 34 ›› Issue (1): 79-85.DOI: 10.16409/j.cnki.2095-039x.2018.01.009

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The Influence of C-terminus Site-directed Mutation on the Toxicity of Bacillus thuringiensis Vip3Aa11 Protein

LUO Guoxing1, LIU Rongmei1, LI Haitao1,2, ZHANG Jinbo1, GAO Jiguo1, ZHANG Jie1,2   

  1. 1. College of Life Sciences, Northeast Agricultural University, Harbin 150030, China;
    2. State Key Laboratory for Biology of Plant Diseases and Insect Pests/Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
  • Received:2017-01-29 Online:2018-02-08 Published:2018-02-06

Abstract: Vegetative insecticidal proteins (VIPs) of Bacillus thuringiensis show a wide insecticidal spectrum against a wide variety of lepidopteran pests. The insecticidal activity and specificity of the Vip3Aa protein derived from different Bt strains are highly different, although the similarities between these proteins are higher than 95%. To determine whether the residues from the Vip3Aa11 C-terminus contribute to the insecticidal activity, three mutants (S543N, D547E and T681V) of Vip3Aa11 were constructed by site directed mutagenesis. Through SDS-PAGE, the mutants produced a 88 kD fusion protein, indicating that all mutants had successful expression in E. coli. Bioassay detection indicated that the insecticidal activity of the S543N mutant against Spodoptera exigua increased obviously, and the LC50value was approximately 5-fold higher than that of the Vip3Aa11, while the activity of D547E mutant against S. exigua decreased obviously. The activities of all the mutants against Helicoverpa armigera had no obvious changes. The results indicated that the site directed mutagenesis of some amino acids from Vip3Aa11 C terminus had an effect on insecticidal activity, and the effect was not consistent against different Lepidopteran pests even in the same mutant. In this study, the differences of insecticidal activity between Vip3Aa11 and mutant proteins serve a guideline for the study of Vip3Aa protein structure and activity mechanism.

Key words: Bacillus thuringiensis, vegetative insecticidal proteins, site directed mutation, activity

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