大肠杆菌tyrR基因对aroP的表达调控(英文)  

Regulation of aroP Expression by tyrR gene in Escherichia coli

作　　者：王建刚[1] 范长胜[1] 吴永庆[1] 金瑞良[1] 刘东信[1] 商量[1] 江培翃[2] 

机构地区：[1]复旦大学生命科学学院微生物学系,上海200433 [2]复旦大学生命科学学院生物化学系,上海200433

出　　处：《生物化学与生物物理学报》2003年第11期993-997,共5页

基　　金：国家自然科学基金资助项目 (No .3 0 0 70 0 2 0 )~~

摘　　要：大肠杆菌的tyrR基因编码芳香氨基酸生物合成和运输途径中的一种全局性调控蛋白质 ,该蛋白质控制着包括自身编码基因tyrR在内的涉及苯丙氨酸、酪氨酸、色氨酸合成与运输的 8个转录单位的转录。大肠杆菌aroP基因编码一种跨质膜主动运输芳香氨基酸的透性酶 ,其转录也受TyrR蛋白抑制。利用PCR反应从E .coliK1 2基因组中分别克隆了aroP(p)基因 (携带自身的启动子 )、aroP基因 (不携带自身的启动子 )和tyrR基因 ,并将它们导入苯丙氨酸生产菌E .coliWT5中。通过大细胞法检测到这 3个基因的表达 ,并分别测定了相应的酶活力。结果发现导入aroP(p)和aroP基因的大肠杆菌吸收苯丙氨酸的能力分别提高到原来的 1 .4 0和 1 .4 6倍 ,这表明利用 pλPR质粒能够表达aroP基因 ,该质粒中的λ右向启动子(PR)和aroP自身启动子 (p)的表达效率几乎同样 ;导入tyrR基因的E .coliWT5ATP酶活力提高到原来的 1 .6 9倍。将两种基因串联克隆在同一质粒中共表达时 ,携带aroP tyrR串联的大肠杆菌株运输苯丙氨酸的能力明显高于携带aroP(p) tyrR串联的大肠杆菌株。以E .coliWT5为对照 ,其AroP的活性定为 1 ,前者的AroP相对酶活力为 1 .31 ,后者为 0 .95 ,这一结果显示TyrR蛋白可能是通过与aroP基因自身启动子的结合作用来负调控aroP基因的?tyrR gene encodes a global regulatory protein (TyrR), which plays an important role in the transcriptional regulation of eight transcription units (including tyrR gene itself) whose protein products catalyze key steps in aromatic amino acid biosynthesis and/or transport. The aroP gene encodes an integral membrane protein (AroP) that transports aromatic amino acids through the cell membrane. The transcription of aroP was reported to be repressed by TyrR. In this work, aroP (p) (aroP gene carrying its own promoter), aroP (aroP gene without promoter) and tyrR genes were amplified by PCR from genomic DNA of E. coli K12 and introduced into E. coli WT5. The expression of aroP and tyrR were detected and the activities of AroP and TyrR were determined. The introduction of either aroP(p) or aroP elevated the strain’s transport activity by 1.40 or 1.46 fold respectively. Transformant carrying tyrR gene showed an ATPase activity 1.69 fold compared with the control. When the genes were linked in tandem and co expressed in a plasmid, the relative AroP transport activity of the strain harboring aroP(p) tyrR (0.95) was significantly lower than that of aroP tyrR (1.31). The results indicated that TyrR might be able to reduce the expression of aroP gene by binding with the aroP promoter region in E. coli.

关 键 词：大肠杆菌 tyrR 基因 aroP 芳香氨基酸 生物合成 代谢调控 苯丙氨酸运输 

分 类 号：Q786[生物学—分子生物学]