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首页> 外文期刊>Peptides: An International Journal >Single amino acid insertions in extracellular loop 2 of Bombyx mori ABCC2 disrupt its receptor function for Bacillus thuringiensis Cry1Ab and Cry1Ac but not Cry1Aa toxins
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Single amino acid insertions in extracellular loop 2 of Bombyx mori ABCC2 disrupt its receptor function for Bacillus thuringiensis Cry1Ab and Cry1Ac but not Cry1Aa toxins

机译：家蚕ABCC2胞外环2中的单个氨基酸插入破坏其对苏云金芽孢杆菌Cry1Ab和Cry1Ac的受体功能，但不会破坏Cry1Aa毒素

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摘要

In a previous report, seven Cry1Ab-resistant strains were identified in the silkworm, Bombyx mori; these strains were shown to have a tyrosine insertion at position 234 in extracellular loop 2 of the ABC transporter C2 (BmABCC2). This insertion was confirmed to destroy the receptor function of BmABCC2 and confer the strains resistance against Cry1Ab and Cry1Ac. However, these strains were susceptible to Cry1Aa. In this report, we examined the mechanisms of the loss of receptor function of the transporter by expressing mutations in Sf9 cells. After replacement of one or two of the five amino acid residues in loop 2 of the susceptible BmABCC2 gene [BmABCC2_S] with alanine, cells still showed susceptibility, retaining the receptor function. Five mutants with single amino acid insertions at position 234 in BmABCC2 were also generated, resulting in loop 2 having six amino acids, which corresponds to replacing the tyrosine insertion in the resistant BmABCC2 gene [BmABCC2_R(+Y-234)] with another amino acid. All five mutants exhibited loss of function against Cry1Ab and Cry1Ac. These results suggest that the amino acid sequence in loop 2 is less important than the loop size (five vs. six amino acids) or loop structure for Cry1Ab and Cry1Ac activity. Several domain-swapped mutant toxins were then generated among Cry1Aa, Cry1Ab, and Cry1Ac, which are composed of three domains. Swapped mutants containing domain II of Cry1Ab or Cry1Ac did not kill Sf9 cells expressing BmABCC21R(+Y-234), suggesting that domain II of the Cry toxin is related to the interaction with the receptor function of BmABCC2. This also suggests that different reactions against Bt-toxins in some B. mori strains, that is, Cry1Ab resistance or Cry1Aa susceptibility, are attributable to structural differences in domain II of Cry1A toxins. (C) 2016 Published by Elsevier Inc.
机译：在以前的报告中，在家蚕中鉴定出7种对Cry1Ab耐药的菌株。这些菌株显示出在ABC转运蛋白C2（BmABCC2）的细胞外环2的234位具有酪氨酸插入。证实该插入破坏了BmABCC2的受体功能，并赋予了菌株对Cry1Ab和Cry1Ac的抗性。但是，这些菌株对Cry1Aa敏感。在本报告中，我们通过在Sf9细胞中表达突变来研究转运蛋白受体功能丧失的机制。用丙氨酸替换易感BmABCC2基因[BmABCC2_S]的2环中5个氨基酸残基中的1个或2个后，细胞仍表现出敏感性，保留了受体功能。还生成了五个在BmABCC2的234位插入单个氨基酸的突变体，从而导致环2具有六个氨基酸，这对应于用另一个氨基酸替换了在抗性BmABCC2基因[BmABCC2_R（+ Y-234）]中的酪氨酸插入。所有五个突变体均表现出针对Cry1Ab和Cry1Ac的功能丧失。这些结果表明，对于Cry1Ab和Cry1Ac活性，环2中的氨基酸序列不如环大小（5个氨基酸对6个氨基酸）或环结构重要。然后在Cry1Aa，Cry1Ab和Cry1Ac之间生成了几种域交换的突变毒素，它们由三个域组成。交换突变体包含Cry1Ab或Cry1Ac的域II不会杀死表达BmABCC21R（+ Y-234）的Sf9细胞，这表明Cry毒素的域II与BmABCC2受体功能的相互作用有关。这也表明在某些B. mori菌株中针对Bt毒素的不同反应，即Cry1Ab抗性或Cry1Aa敏感性，可归因于Cry1A毒素结构域II的结构差异。 （C）2016由Elsevier Inc.发布

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