Nucleic Acids Research Advance Access originally published online on February 6, 2007
Nucleic Acids Research 2007 35(5):1432-1440; doi:10.1093/nar/gkl1142
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Nucleic Acids Research, 2007, Vol. 35, No. 5 1432-1440
© 2007 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
Interplay between CRP-cAMP and PII-Ntr systems forms novel regulatory network between carbon metabolism and nitrogen assimilation in Escherichia coli
1National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, P. R. China, 2Department of Biological Science, Imperial College of Science, Technology and Medicine, London SW72AZ, UK and 3Unité des Régulations Transcriptionnelles, URA-CNRS 2172, Institut Pasteur, 75724 Paris, France
*To whom correspondence should be addressed. Tel: +86 10 6275 8490; Fax: +86 10 6275 6325; Email: wangyp{at}pku.edu.cn
Received November 21, 2006. Revised December 13, 2006. Accepted December 14, 2006.
In Escherichia coli, utilization of carbon sources is regulated by the phosphoenolpyruvate-dependent phosphotransferase system (PTS), which modulates the intracellular levels of cAMP. The cAMP receptor protein (CRP) controls the transcription of many catabolic genes. The availability of nitrogen is sensed by the PII protein at the level of intracellular glutamine. Glutamine is transported mainly by GlnHPQ, and synthesized by glutamine synthetase (GS) encoded by glnA. Previous studies suggest that CRP affects nitrogen assimilation. Here we showed that at least two mechanisms are involved. First, CRP activates glnHp1 via synergistic binding with sigma 70 RNA polymerase (E
70) and represses glnHp2. As a consequence, in the presence of glutamine, the overall enhancement of glnHPQ expression alters GlnB signalling and de-activates glnAp2. Second, in vitro studies show that CRP can be recruited by sigma 54 holoenzyme (E54) to a site centred at –51.5 upstream of glnAp2. CRP-induced DNA-bending prevents the nitrogen regulation protein C (NtrC) activator from approaching the activator-accessible face of the promoter-bound E54 closed complex, and inhibits glnAp2. Therefore, as the major transcriptional effector of the ‘glucose effect’, CRP affects both the signal transduction pathway and the overall geometry of the transcriptional machinery of components of the nitrogen regulon.
4Present address: Yi-Xin Huo, Department of Chemistry and Biochemistry and The Molecular Biology Institute, University of California, Los Angeles, P.O. Box 951569, 90095, USA
The authors wish it to be known that, in their opinion, the first two should be regarded as joint First Authors.
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