De Reuse H, Danchin A
Unité Régulation de l'Expression Génétique, Institut Pasteur, Paris, France.
J Bacteriol. 1991 Jan;173(2):727-33. doi: 10.1128/jb.173.2.727-733.1991.
The pts operon of Escherichia coli is composed of the genes ptsH, ptsI, and crr, which code for three proteins of the phosphoenolpyruvate-dependent phosphotransferase system (PTS): the HPr, enzyme I (EI), and EIIIGlc proteins, respectively. These three genes are organized in a complex operon in which the major part of expression of the distal gene, crr, is initiated from a promoter region within ptsI. Expression from the promoter region of the ptsH and ptsI genes has been studied in vivo by using gene fusions with lacZ. Transcription from this promoter region is under the positive control of catabolite activator protein (CAP)-cyclic AMP (cAMP) and is also enhanced during growth in the presence of glucose (a PTS substrate). This report describes a genetic characterization of the mechanism by which growth on glucose causes transcriptional stimulation of the pts operon. This regulation is dependent on transport through the glucose-specific permease of the PTS, EIIGlc. Our results strongly suggest that transcriptional regulation of the pts operon is the consequence of an increase in the level of unphosphorylated EIIGlc which is produced during glucose transport. Furthermore, overproduction of EIIGlc in the absence of transport was found to stimulate expression of the pts operon. We also observed that CAP-cAMP could cause stimulation independently of the EIIGlc and that glucose could activate in the absence of cAMP in a strain overproducing EIIGlc. Our results indicate that glucose acts like an environmental signal through a mechanism of signal transduction. A sequence similarity between the C terminus of EIIGlc and the consensus of transmitter modules of the sensor proteins defined by E. C. Kofoid and J. S. Parkinson (Proc. Natl. Acad. Sci. USA 85:4981-4985, 1988) suggests that EIIGlc might have properties in common with the sensors of the two-component systems.
大肠杆菌的pts操纵子由ptsH、ptsI和crr基因组成，它们分别编码磷酸烯醇丙酮酸依赖性磷酸转移酶系统（PTS）的三种蛋白质：HPr、酶I（EI）和EIIIGlc蛋白。这三个基因组成一个复杂的操纵子，其中远端基因crr的主要表达部分是从ptsI内的一个启动子区域起始的。通过使用与lacZ的基因融合，在体内研究了ptsH和ptsI基因启动子区域的表达。来自该启动子区域的转录受分解代谢物激活蛋白（CAP）-环腺苷酸（cAMP）的正调控，并且在葡萄糖（一种PTS底物）存在下生长期间也会增强。本报告描述了葡萄糖生长导致pts操纵子转录刺激的机制的遗传学特征。这种调控依赖于通过PTS的葡萄糖特异性通透酶EIIGlc的转运。我们的结果强烈表明，pts操纵子的转录调控是葡萄糖转运过程中产生的未磷酸化EIIGlc水平增加的结果。此外，发现在没有转运的情况下过量生产EIIGlc会刺激pts操纵子的表达。我们还观察到，CAP-cAMP可以独立于EIIGlc引起刺激，并且在过量生产EIIGlc的菌株中，葡萄糖可以在没有cAMP的情况下激活。我们的结果表明，葡萄糖通过信号转导机制像环境信号一样起作用。EIIGlc的C末端与E.C.Kofoid和J.S.Parkinson定义的传感器蛋白的传递模块共有序列之间的相似性（美国国家科学院院刊85:4981-4985,1988）表明，EIIGlc可能具有与双组分系统的传感器共同的特性。
