细菌“一种新的分泌机制”初探

构建了免疫毒素DAB389（Gly4Ser）2-αMSH的两种表达质粒,其一为胞内表达质粒pET28a/DAB389（Gly4Ser）2-αMSH,其二为胞周质表达质粒pET20b/DAB389（Gly4Ser）2-αMSH。实验结果显示,置于胞内表达质粒的DAB389（Gly4Ser）2-αMSH在大肠杆菌的周质腔内分泌表达,而置于胞周质表达质粒的DAB389（Gly4Ser）2-αMSH却不能表达。通过分析免疫毒素的特性,发现DAB389（Gly4Ser）2-αMSH中并不存在信号肽序列;与革兰氏阴性细菌中已发现的四种蛋白质分泌途径特性相比较,发现它不属于其中的任何一种,可能为一种新型细菌分泌机制。

A possible secretion system of E.coli

Prokaryotic cytoplasmic and periplasmic expression vectors（pET28a/DAB389（Gly4Ser）2-αMSH and pET20b-DAB389（Gly4Ser）2-αMSH） were constructed to study the expression of immunotoxin DAB389（Gly4Ser）2-αMSH in E.coli respectively.Experimental results indicated that DAB389（Gly4Ser）2-αMSH was directed to periplasmic space of Rosettablue（DE3） with vector pET28a/DAB389（Gly4Ser）2-αMSH,on the other hand,DAB389（Gly4Ser）2-αMSH wasn＇t expressed in Rosettablue（DE3） with vector pET20b-DAB389（Gly4Ser）2-αMSH.Western-blotting showed that the expressed protein could react with the specific horse sera against diphtheria toxin.Through analyzing the characteristic of DAB389（Gly4Ser）2-αMSH with Signal P 3.0 Server（Technical University of Denmark）,the results showed that DAB389（Gly4Ser）2-αMSH didn＇t include signal peptide.Compared with regularity of expression of secretion systems of Gram-negative bacteria,this expression of secretion system didn＇t belong to any of the above mechanisms.Therefore,the following idea that there may be another new expression of secretion system in E.coli was put forward.