Department of Entomology, University of California-Riverside, CA 92521, USA.
Lett Appl Microbiol. 2012 Feb;54(2):88-95. doi: 10.1111/j.1472-765X.2011.03176.x. Epub 2012 Jan 3.
To determine whether the 20-kDa chaperone-like protein of Bacillus thuringiensis ssp. israelensis enhances synthesis, crystallization and solubility of the Cry3A coleopteran toxin and whether the crystalline inclusions produced are toxic to neonates of the Colorado potato beetle, Leptinotarsa decemlineata.
The cry3A gene was expressed in the 4Q7 strain of B. thuringiensis ssp. israelensis in the absence or presence of the 20-kDa gene. The 20-kDa protein enhanced Cry3A yield by 2·7-fold per unit of fermentation medium. Crystal volumes averaged 2·123 and 0·964 μm(3) when synthesized in, respectively, the presence or absence of the 20-kDa protein. Both crystals were soluble at pH 5 and pH 6; however, the larger crystal was 1·7× and 1·5× more soluble at, respectively, pH 7 and pH 10. No significant difference in toxicity against L. decemlineata neonates was observed.
This report demonstrated that the 20-kDa chaperone-like protein enhances yield, volume and solubility of the coleopteran Cry3A crystalline inclusions per unit crystal/spore mixture.
This is the first report showing that an accessory protein (20-kDa) could enhance synthesis and crystallization of Cry3A, a finding that could be beneficial for commercial production of this coleopteran-specific insecticidal protein for microbial insecticides and possibly even for transgenic crops.
确定苏云金芽孢杆菌以色列亚种的 20kDa 热休克蛋白伴侣是否能增强 Cry3A 鞘翅目毒素的合成、结晶和可溶性，以及产生的结晶包含物是否对美洲马铃薯甲虫的幼虫有毒。
在苏云金芽孢杆菌以色列亚种的 4Q7 菌株中，在不存在或存在 20kDa 基因的情况下表达了 cry3A 基因。20kDa 蛋白使发酵培养基中每单位 Cry3A 的产量提高了 2.7 倍。当分别在有和没有 20kDa 蛋白的情况下合成时，晶体体积平均为 2.123 和 0.964 μm(3)。两种晶体在 pH5 和 pH6 下均具有可溶性；然而，在 pH7 和 pH10 下，较大的晶体分别提高了 1.7×和 1.5×的溶解度。对 L. decemlineata 幼虫的毒性没有显著差异。
本报告表明，20kDa 热休克蛋白伴侣样蛋白提高了鞘翅目 Cry3A 晶体包含物的单位晶体/孢子混合物的产量、体积和可溶性。
这是第一个表明辅助蛋白（20kDa）可以增强 Cry3A 合成和结晶的报告，这一发现可能有利于这种鞘翅目特异性杀虫蛋白的商业生产，用于微生物杀虫剂，甚至可能用于转基因作物。
