苏云金杆菌HBF-1菌株晶体蛋白活化及对金龟幼虫毒力的影响

The Activation of Bacillus thuringiensis HBF-1 Strain Parasproal Crystals and the Effects of Toxicity on Chafer Larva

通过SDS-PAGE研究了缓冲液pH值对HBF-1菌株晶体蛋白的降解活化作用及其对晶体蛋白杀虫毒力的影响。结果表明,晶体蛋白在牛胰蛋白酶和金龟子幼虫中肠液作用下的降解程度,随着缓冲液pH值的增加而加深。幼虫中肠蛋白酶在缓冲液pH值达到8.0时,就能完全降解晶体蛋白;而胰蛋白酶在pH值达到11.0时,才能把晶体蛋白完全降解。产生的活力片段分子量近似,均在63.0kD左右。在pH11.0条件下,胰蛋白酶的降解速度大于幼虫中肠液。生测结果显示,晶体蛋白经中肠液水解后,其毒力明显增强,在7d和14d增效率分别达到1.25和1.00。同时,经强碱性缓冲液处理后,也起到了较强的增效作用。

The effects of buffer pH values and dissolution on the proteolysis of Bacillus thuringiensis HBF-1 parasproal crystals are studied by SDS-PAGE. By Incubation with chafer larva midgut juice and bovine trypsin, it was demonstrated that proteolysis of the crystals was increased as buffer pH rose from 4.0 to 11.0. And the parasporal crystals could be completely degraded by larval midgut protease at pH 8.0 in comparison with by bovine trypsin at pH 11.0. Molecular weight of the active proteolytic product was about 63.0 kD. Bioassay suggested that toxicity of crystals was increased by 125 % and 100% at 7 d and 14 d, respectively, when the crystals was proteolysed by larva midgut juice.