人b防御素3和植物des-pGLu1-brazzein融合蛋白表达菌的诱导条件优化及其活性分析

对人b防御素3和植物甜蛋白des-pGlu1-Brazzein嵌合基因的工程菌株BL-pET-hBD3-Bra的IPTG诱导表达条件进行了研究, 同时对所表达的目的蛋白进行了纯化和活性分析。IPTG浓度、诱导时间和诱导温度对菌株生长和目的蛋白表达的试验结果显示: 所取的IPTG浓度(0.2~1.0 mmol/L)对菌株生长和目的蛋白的表达无显著影响(P>0.05); 菌株的生物量随着诱导时间的延长而增加, 6 h优于4 h(P<0.01), 但是蛋白的表达量无明显增加(P>0.05); 其中温度是重要的影响因素, 在30°C诱导时, 目的蛋白的表达量占总蛋白的35%左右。进一步的研究表明, 菌株在30°C~32°C生长, 在 30°C诱导最优。对目的蛋白的活性分析表明, 所得到的hBD3-Bra融合蛋白有甜味, 其甜度大约是蔗糖的200倍, 但是其杀菌活性很弱, 经凝血酶切割后, des-pGlu1-Brazzein的甜度大大提高, 大约为蔗糖甜度的600倍, 重组hBD3对大肠杆菌和金黄色葡萄球菌有明显的抑菌活性。

Optimizing Conditions for the Expression of Human b Defensin 3 and des-pGlu1-Brazzein in Escherichia coli and Analysis of Their Activity

The inductive conditions for the flask-shaking of E.coli BL21-pET-hBD3-Bra had been optimized, at the same time, the expressed protein had been purified and analyzed. The effect of three factors which were IPTG concentration, induction time and temperature on growth of strain and on the yield of hBD3-Bra was analyzed in detail. The result indicated that the concentration of IPTG had little effect on the growth and the expression of target protein between 0.2-1 mmol/L, Biomass would be improved as time passed, but the target protein didn't increase obviously as the same time, temperature was the most important factor, the expressed level of hBD3-Bra, as high as about 35% of total cell protein, could be gained when strain was induced by IPTG under 30 degrees C. Further analysis showed the best temperature for growth was 30 degrees C-32 degrees C and for expression protein was 30 degrees C.The purified hBD3-Bra has a weak antimicrobial activity, but is 200 times sweeter than that of sucrose. After digested by thrombin and purified by affinity column, the natural des-pGlul-Brazzein also has 600-time sweetness of sucrose, and the recombinant hBD3 has a high antimicrobial activity again E. coli and S. aureus.