Characterization of the Novel Insecticidal Crystal Protein Cyt3Aa1 from &amp;lt;i&amp;gt;Bacillus thuringiensis&amp;lt;/i&amp;gt; TD516

Jun Zhu,Shuangcheng Li,Lingxia Wang,Aiping Zheng,Ping Li,Huainian Liu,Shiquan Wang,Zizhong Zhu,Aijun Wang,Baoli Zhang,Qiming Deng,Yiping Liu,Xu Liu,Ting Zou,Yueyang Liang

doi:10.4236/aim.2020.107025

Abstract

Bacillus thuringiensis (Bt) produces two families of insecticidal crystal proteins, i.e., crystalline (Cry) and cytolytic (Cyt) toxins. Cyt3Aa1, the newest Cyt family member, is produced by Bt TD516. Bioassay results have shown that Cyt3Aa1 has weak hemolytic activity against human red blood cells and is not toxic to A. aegypti larvae, but causing a teratogenic effect. The three-dimensional structure of Cyt3Aa1 has a typical cytolysin fold containing a β-sheet held by two surrounding α-helical layers, resembling the previously reported Cyt1Aa and Cyt2Aa structures, which indicated that Cyt3Aa1 might be a membrane-perforation toxin and could induce synergism with Cry protein. This study provides a new source of insecticidal crystal proteins, and presents a foundation for understanding the biological characterization of it, which will aid in the development of strategies to cope with the potential problem of insect resistance.

Highlights

During sporulation, Bacillus thuringiensis (Bt) produces two families of insecticidal crystal proteins, Cry and Cyt
The three-dimensional structure of Cyt3Aa1 has a typical cytolysin fold containing a β-sheet held by two surrounding α-helical layers, resembling the previously reported Cyt1Aa and Cyt2Aa structures, which indicated that Cyt3Aa1 might be a membrane-perforation toxin and could induce synergism with Cry protein
This study provides a new source of insecticidal crystal proteins, and presents a foundation for understanding the biological characterization of it, which will aid in the development of strategies to cope with the potential problem of insect resistance

Summary

Introduction

Bt produces two families of insecticidal crystal proteins, Cry and Cyt. The Cyt proteins mainly have activity against larvae of Diptera, Hemiptera, and Aphidinae [5] [6] [7]. The Cyt1Aa and Cyt2Aa can synergize Cry and Vip toxicity against mosquitoes, respectively [7] [8] [9], and Cyt toxin may ease the threat of insect resistance [10]. The crystal structures of Cyt1Aa and Cyt2Aa have been determined by X-ray crystallography, and both have a single α/β domain composed of two outer layers of α-helix hairpins wrapped around a β-sheet [2] [3]. The analysis of the structural characterization of Cyt protein could bridge the structure-knowledge gap

Methods

Results

Conclusion