One advantage of using the Cry proteins of Bacillus thuringiensis as pesticides is their relatively narrow spectrum of activity, thus reducing the risk of non-target effects. Understanding the molecular basis of specificity has the potential to help us design improved products against emerging pests, or against pests that have developed resistance to other Cry proteins. Many previous studies have associated specificity with the binding of the Cry protein, particularly through the apical regions of domain II, to particular receptors on the midgut epithelial cells of the host insect. We have previously found that the specificity of Cry2A proteins against some insects is associated with domain I, which is traditionally associated with pore-formation but not receptor binding. In this work we identify four amino acids in the N-terminal region that, when mutated, can confer activity towards Aedes aegypti to Cry2Ab, a protein known to lack this toxicity. Intriguingly these amino acids are located in the region (amino acids 1–49) that is believed to be removed during proteolytic activation of the Cry protein. We discuss how the motifs containing these amino acids might be involved in the toxic process.

使用苏云金芽孢杆菌Cry蛋白的优势之一因为杀虫剂的活性谱相对较窄，因此降低了非靶标作用的风险。了解特异性的分子基础有可能帮助我们设计针对新出现的有害生物或对其他Cry蛋白产生抗性的有害生物的改良产品。先前的许多研究都与Cry蛋白的结合（特别是通过结构域II的顶端区域）与宿主昆虫中肠上皮细胞上的特定受体的结合相关，具有特异性。我们先前发现，Cry2A蛋白对某些昆虫的特异性与结构域I有关，而结构域I通常与孔形成有关，但与受体结合无关。在这项工作中，我们确定了N中的四个氨基酸-突变的末端区域可以赋予埃及伊蚊活性至Cry2Ab，Cry2Ab是一种已知缺乏这种毒性的蛋白质。有趣的是，这些氨基酸位于Cry蛋白的蛋白水解激活过程中被除去的区域（第1至49个氨基酸）。我们讨论了包含这些氨基酸的基序可能如何参与毒性过程。