The role of β18-β19 loop structure in insecticidal activity of Cry1Ac toxin from Bacillus thuringiensis  

作　　者：XIA LiQiu WANG FaXiang DING XueZhi ZHAO XinMin FU ZuJiao QUAN MeiFang YU ZiNiu 

机构地区：[1]Key Laboratory of Microbial Molecular Biology of Hunan Province, College of Life Science, Hunan Normal University, Changsha 410081, China [2]State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China

出　　处：《Chinese Science Bulletin》2008年第20期3178-3184,共7页

基　　金：the National High Technology Research and Development Program of China (Grant No. 2006AA02Z187, 2006AA10A212);National Natural Science Foundation of China (Grant No. 30670052);Ph.D. Programs Foundation of Ministry of Education of China (Grant No. 20060452006)

摘　　要：The β18-β19 loop in domain III of Cry1Ac toxin is unique among Bacillus thuringiensis Cry proteins. In this study, the role of the loop structure in insecticidal activity of Cry1Ac toxin was investigated. Alanine scanning mutations within the loop were initially generated and most mutants were over-expressed and reduced toxicity at different degrees, except mutant N546A that showed almost 2 times enhanced toxicity against Helicoverpa armigera larvae. Further mutagenic analysis of N546 revealed that a charged amino acid in this position would cause very unfavorable influence on insecticidal activity. In addition, the deletion of N546 led to protein instability because of destruction of the loop integrity. Besides, mutant W544F was much more toxic than W544Y, indicating that hydrophobic nature of the position was important for maintaining the stability and activity of Cry1Ac protein. These findings are the first biological evidence for a structural function of β18-β19 loop in insecticidal activity of the Cry1Ac toxin.The β18-β19 loop in domain Ⅲ of Cry1Ac toxin is unique among Bacillus thuringlensis Cry proteins. In this study, the role of the loop structure in insecticidal activity of Cry1Ac toxin was investigated. Alanine scanning mutations within the loop were initially generated and most mutants were over-expressed and reduced toxicity at different degrees, except mutant N546A that showed almost 2 times enhanced toxicity against Helicoverpa armigera larvae. Further mutagenic analysis of N546 revealed that a charged amino acid in this position would cause very unfavorable influence on insecticidal activity. In addition, the deletion of N546 led to protein instability because of destruction of the loop integrity. Besides, mutant W544F was much more toxic than W544Y, indicating that hydrophobic nature of the position was important for maintaining the stability and activity of Cry1Ac protein. These findings are the first biological evidence for a structural function of β18-β19 loop in insecticidal activity of the Cry1Ac toxin.

关 键 词：苏云金芽孢杆菌 CRY1AC 杀虫剂 杀虫活性 环结构 天冬酰胺酸 色氨酸 

分 类 号：S482.3[农业科学—农药学]