Lu Keyu, Gu Yuqing, Liu Xiaoping, Lin Yi, Yu Xiao-Qiang
Fujian Provincial Key Laboratory of Biochemical Technology, Department of Bioengineering and Biotechnology, College of Chemical Engineering, Huaqiao University , Xiamen, Fujian 361021, People's Republic of China.
Division of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City , Kansas City, Missouri 64110, United States.
J Agric Food Chem. 2017 Mar 15;65(10):2048-2055. doi: 10.1021/acs.jafc.6b05769. Epub 2017 Mar 2.
Cry toxins are insecticidal toxin proteins produced by a spore-forming Gram-positive bacterium Bacillus thuringiensis. Interactions between the Cry toxins and the receptors from midgut brush border membrane vesicles (BBMVs), such as cadherin, alkaline phosphatase, and aminopeptidase, are key steps for the specificity and insecticidal activity of Cry proteins. However, little is known about the midgut juice proteins that may interfere with Cry binding to the receptors. To validate the hypothesis that there exist Cry-binding proteins that can interfere with the insecticidal process of Cry toxins, we applied Cry1Ab1-coupled Sepharose beads to isolate Cry-binding proteins form midgut juice of Plutella xylostella and Spodoptera exigua. Trypsin-like serine proteases and Dorsal were found to be Cry1Ab1-binding proteins in the midgut juice of P. xylostella. Peroxidase-C (POX-C) was found to be the Cry1Ab1-binding protein in the midgut juice of S. exigua. We proposed possible insecticidal mechanisms of Cry1Ab1 mediated by the two immune-related proteins: Dorsal and POX-C. Our results suggested that there exist, in the midgut juice, Cry-binding proteins, which are different from BBMV-specific receptors.
晶体毒素是由形成芽孢的革兰氏阳性细菌苏云金芽孢杆菌产生的杀虫毒素蛋白。晶体毒素与中肠刷状缘膜囊泡（BBMVs）中的受体（如钙黏蛋白、碱性磷酸酶和氨肽酶）之间的相互作用是决定晶体蛋白特异性和杀虫活性的关键步骤。然而，对于可能干扰晶体蛋白与受体结合的中肠液蛋白却知之甚少。为了验证存在能够干扰晶体毒素杀虫过程的晶体结合蛋白这一假说，我们使用偶联了Cry1Ab1的琼脂糖珠从小菜蛾和甜菜夜蛾的中肠液中分离晶体结合蛋白。结果发现，类胰蛋白酶丝氨酸蛋白酶和背蛋白是小菜蛾中肠液中的Cry1Ab1结合蛋白。过氧化物酶-C（POX-C）是甜菜夜蛾中肠液中的Cry1Ab1结合蛋白。我们提出了由两种免疫相关蛋白——背蛋白和POX-C介导的Cry1Ab1可能的杀虫机制。我们的结果表明，中肠液中存在与BBMV特异性受体不同的晶体结合蛋白。
