Lövgren A, Zhang M, Engström A, Dalhammar G, Landén R
Department of Microbiology, University of Stockholm, Sweden.
Mol Microbiol. 1990 Dec;4(12):2137-46. doi: 10.1111/j.1365-2958.1990.tb00575.x.
The gene for the secreted neutral metalloprotease, immune inhibitor A (InA), from Bacillus thuringiensis var. alesti has been cloned and sequenced. The deduced amino acid sequence has been confirmed by partial amino acid sequencing. The central part of the amino acid sequence showed similarity to the active site in thermolysin. Southern and Western blots show that InA-related sequences are common among other B. thuringiensis subspecies. In Western blots, 17 out of 25 tested species gave a positive signal. Culture filtrates from subspecies expressing InA were toxic when injected in Trichoplusia ni larvae, whereas filtrate from a strain negative in Western blot had no effect when injected. The LD50 dose of purified InA protein injected in T. ni larvae was 12.5 +/- 2.5 ng per mg of larval body weight.
来自苏云金芽孢杆菌变种阿莱亚种的分泌型中性金属蛋白酶免疫抑制剂A（InA）基因已被克隆和测序。推导的氨基酸序列已通过部分氨基酸测序得到证实。氨基酸序列的中部显示出与嗜热菌蛋白酶的活性位点相似。Southern印迹和Western印迹表明，InA相关序列在其他苏云金芽孢杆菌亚种中很常见。在Western印迹中，25个测试物种中有17个给出了阳性信号。注射表达InA的亚种的培养滤液对烟草天蛾幼虫有毒，而Western印迹呈阴性的菌株的滤液注射后则没有效果。注射到烟草天蛾幼虫体内的纯化InA蛋白的半数致死剂量为每毫克幼虫体重12.5±2.5纳克。
