Brøndsted L, Atlung T
Department of Microbiology, Technical University of Denmark, Lyngby, Denmark.
J Bacteriol. 1996 Mar;178(6):1556-64. doi: 10.1128/jb.178.6.1556-1564.1996.
The expression and transcriptional regulation of the Escherichia coli cyx-appA operon and the appY gene have been investigated under different environmental conditions with single-copy transcriptional lacZ fusions. The cyx-appA operon encodes acid phosphatase and a putative cytochrome oxidase. ArcA and AppY activated transcription of the cyx-appA operon during entry into stationary phase and under anaerobic growth conditions. The expression of the cyx-appA operon was affected by the anaerobic energy metabolism. The presence of the electron acceptors nitrate and fumarate repressed the expression of the cyx-appA operon. The nitrate repression was partially dependent on NarL. A high level of expression of the operon was obtained in glucose medium supplemented with formate, in which E. coli obtains energy by fermentation. The formate induction was independent of the fhlA gene product. The results presented in this paper indicate a clear difference in the regulation of the cyx-appA operon and that of the cyd operon, encoding the cytochrome d oxidase complex. The results suggest that cytochrome x oxidase has a function under even more-oxygen-limiting conditions than cytochrome d oxidase. The expression of the appY gene is induced immediately by anaerobiosis, and this anaerobic induction is independent of Fnr, and AppY, but dependent on ArcA. The expression of the appY gene is not affected significantly by the anaerobic energy metabolism, i.e., fermentation versus anaerobic respiration. A model incorporating the anaerobic regulation of the appY gene and the two operons which are controlled by AppY, the hydrogenase 1 (hya) operon and the acid phosphatase (cyx-appA) operon, is presented. The expression of the appY gene is inversely correlated with the growth rate and is induced by phosphate starvation as well as during entry into stationary phase. During oxygen-limiting conditions the stationary-phase induction is partially dependent on ArcA. The alternative sigma factor sigma S has limited influence on the transcription of the appY gene during entry into stationary phase and no effect on the induction by phosphate starvation.
利用单拷贝转录lacZ融合技术，研究了大肠杆菌cyx - appA操纵子和appY基因在不同环境条件下的表达及转录调控。cyx - appA操纵子编码酸性磷酸酶和一种假定的细胞色素氧化酶。在进入稳定期和厌氧生长条件下，ArcA和AppY激活cyx - appA操纵子的转录。cyx - appA操纵子的表达受厌氧能量代谢的影响。电子受体硝酸盐和富马酸盐的存在抑制了cyx - appA操纵子的表达。硝酸盐抑制部分依赖于NarL。在补充了甲酸盐的葡萄糖培养基中可获得该操纵子的高水平表达，在此培养基中大肠杆菌通过发酵获取能量。甲酸盐诱导不依赖于fhlA基因产物。本文给出的结果表明，cyx - appA操纵子与编码细胞色素d氧化酶复合物的cyd操纵子在调控上存在明显差异。结果表明，细胞色素x氧化酶在比细胞色素d氧化酶更严格的氧限制条件下起作用。appY基因的表达在厌氧状态下立即被诱导，这种厌氧诱导不依赖于Fnr和AppY，但依赖于ArcA。appY基因的表达不受厌氧能量代谢（即发酵与厌氧呼吸）的显著影响。提出了一个包含appY基因的厌氧调控以及由AppY控制的两个操纵子（氢化酶1（hya）操纵子和酸性磷酸酶（cyx - appA）操纵子）的模型。appY基因的表达与生长速率呈负相关，并且在磷酸盐饥饿以及进入稳定期时被诱导。在氧限制条件下，稳定期诱导部分依赖于ArcA。替代西格玛因子西格玛S在进入稳定期时对appY基因的转录影响有限，对磷酸盐饥饿诱导无影响。
