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Multidimensional annotation of the Escherichia coli K-12 genome 总被引:2,自引:0,他引:2
Karp PD Keseler IM Shearer A Latendresse M Krummenacker M Paley SM Paulsen I Collado-Vides J Gama-Castro S Peralta-Gil M Santos-Zavaleta A Peñaloza-Spínola MI Bonavides-Martinez C Ingraham J 《Nucleic acids research》2007,35(22):7577-7590
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Regulation of the citrate synthase (gltA) gene of Escherichia coli in response to anaerobiosis and carbon supply: role of the arcA gene product. 总被引:7,自引:5,他引:2 下载免费PDF全文
As an enzyme of the tricarboxylic acid cycle pathway, citrate synthase participates in the generation of a variety of cellular biosynthetic intermediates and in that of reduced purine nucleotides that are used in energy generation via electron transport-linked phosphorylation reactions. It catalyzes the condensation of oxaloacetate and acetyl coenzyme A to produce citrate plus coenzyme A. In Escherichia coli this enzyme is encoded by the gltA gene. To investigate how gltA expression is regulated, a gltA-lacZ operon fusion was constructed and analyzed following aerobic and anaerobic cell growth on various types of culture media. Under aerobic culture conditions, expression was elevated to a level twofold higher than that reached under anaerobic culture conditions. ArcA functions as a repressor of gltA expression under each set of conditions: in a delta arcA strain, gltA-lacZ expression was elevated to levels two- and eightfold higher than those seen in a wild-type strain under aerobic and anaerobic conditions, respectively. This control is independent of the fnr gene product, an alternative anaerobic gene regulator in E. coli. When the richness or type of carbon compound used for cell growth was varied, gltA-lacZ expression varied by 10- to 14-fold during aerobic and anaerobic growth. This regulation was independent of both the crp and fruR gene products, suggesting that another regulatory element in E. coli is responsible for the observed control. Finally, gltA-lacZ expression was shown to be inversely proportional to the cell growth rate. These findings indicate that the regulation of gltA gene expression is complex in meeting the differential needs of the cell for biosynthesis and energy generation under various cell culture conditions. 相似文献
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Maas WK 《BioEssays : news and reviews in molecular, cellular and developmental biology》2007,29(5):484-488
The present account spans the history of arginine regulation from its discovery in 1955 until the present. In 1957 I demonstrated that not only added arginine but also internally produced arginine represses enzyme formation and that the potential for enzyme synthesis is in excess of what is required for growth. In 1959 I located the regulatory gene argR encoding the arginine repressor. An unusual feature of this research was the finding that in E. coli B, in contrast to E. coli K12, arginine synthesis is permanently repressed, independent of arginine. This was due to a single amino acid difference between the two repressors. Recent studies showed that, in natural populations of E. coli, K12-type regulation is much more frequent than B-type regulation, and that E. coli B evolved from a strain with K12-type regulation. In competition experiments, E. coli K12 was found to be favored in the presence of arginine and E. coli B in its absence, showing that contrary to expectations permanently turned off regulation is favored over negative regulation in some environments. 相似文献