Liang Y, Dean D H
Department of Biochemistry, Ohio State University, Columbus 43210.
Mol Microbiol. 1994 Aug;13(4):569-75. doi: 10.1111/j.1365-2958.1994.tb00451.x.
The Bacillus thuringiensis insecticidal crystal protein CryIIA has both high mosquito activity and gypsy moth activity; in contrast CryIIB, which is 87% homologous, displays no mosquito activity and has a three-fold lower gypsy moth activity. The regions responsible for specificity against gypsy moth (Lymantria dispar) and mosquito (Aedes aegypti) larvae were located by introducing MluI and XhoI sites into homologous positions within the putative domain II of both cryIIA and cryIIB genes, which divided almost equally the respective second domains into three regions. Taking advantage of naturally occurring NheI and NarI sites that border the putative domain II, a set of seven chimeric proteins were produced by exchanging all combinations of those regions between CryIIA and CryIIB. Analysis of the toxicity of these chimeric proteins demonstrated that the lepidopteran and dipteran specificity regions of CryIIA were not colinear. While the specificity region of CryIIA against mosquito larvae involved region 1 and probably also region 2, the specificity region of CryIIA against gypsy moth larvae was located within region 2.
苏云金芽孢杆菌杀虫晶体蛋白CryIIA对蚊子和舞毒蛾均具有高活性；相比之下，与之有87%同源性的CryIIB对蚊子无活性，对舞毒蛾的活性则低三倍。通过将MluI和XhoI位点引入cryIIA和cryIIB基因推定结构域II内的同源位置来确定对舞毒蛾（舞毒蛾属）和蚊子（埃及伊蚊）幼虫具有特异性的区域，这几乎将各自的第二个结构域平均分为三个区域。利用与推定结构域II相邻的天然存在的NheI和NarI位点，通过交换CryIIA和CryIIB之间这些区域的所有组合产生了一组七种嵌合蛋白。对这些嵌合蛋白毒性的分析表明，CryIIA的鳞翅目和双翅目特异性区域并非共线。虽然CryIIA对蚊子幼虫的特异性区域涉及区域1，可能还涉及区域2，但CryIIA对舞毒蛾幼虫的特异性区域位于区域2内。
