This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Tramonti, A.
Right arrow Articles by De Biase, D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Tramonti, A.
Right arrow Articles by De Biase, D.

 Previous Article  |  Next Article 

Journal of Bacteriology, December 2006, p. 8118-8127, Vol. 188, No. 23
0021-9193/06/$08.00+0     doi:10.1128/JB.01044-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Mechanisms of Transcription Activation Exerted by GadX and GadW at the gadA and gadBC Gene Promoters of the Glutamate-Based Acid Resistance System in Escherichia coli{triangledown}

Angela Tramonti,1,2 Michele De Canio,2 Isabel Delany,3 Vincenzo Scarlato,3,4 and Daniela De Biase2*

Istituto di Biologia e Patologia Molecolari, CNR,1 Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Scienze Biochimiche "A. Rossi Fanelli," Università di Roma La Sapienza, Roma, Italy,2 Molecular Immunology Unit, Chiron Vaccines, Siena, Italy,3 Dipartimento di Biologia, Università di Bologna, Bologna, Italy4

Received 17 July 2006/ Accepted 7 September 2006

In Escherichia coli the gad system protects the cell from the extreme acid stress encountered during transit through the host stomach. The structural genes gadA, gadB, and gadC encode two glutamate decarboxylase isoforms and a glutamate/{gamma}-aminobutyrate (GABA) antiporter, respectively. Glutamate decarboxylation involves both proton consumption and production of GABA, a neutral compound which is finally exported via the GadC antiporter. Regulation of gadA and gadBC transcription is very complex, involving several circuits controlling expression under different growth phase, medium, and pH conditions. In this study we found that the AraC-like activators GadX and GadW share the same 44-bp binding sites in the gadA and gadBC regulatory regions. The common binding sites are centered at 110.5 bp and 220.5 bp upstream of the transcriptional start points of the gadA and gadBC genes, respectively. At the gadA promoter this regulatory element overlaps one of the binding sites of the repressor H-NS. The DNA of the gadBC promoter has an intrinsic bend which is centered at position –121. These findings, combined with transcriptional regulation studies, may account for the two different mechanisms of transcriptional activation by GadX and GadW at the two promoters studied. We speculate that while at the gadA promoter GadX and GadW activate transcription by displacing H-NS via an antirepressor mechanism, at the gadBC promoter the mechanism of activation involves looping of the DNA sequence between the promoter and the activator binding site.

* Corresponding author. Mailing address: Dipartimento di Scienze Biochimiche "A. Rossi Fanelli," Università di Roma La Sapienza, Piazzale Aldo Moro 5, 00185 Roma, Italy. Phone: (39) 06 4991 7692. Fax: (39) 06 4991 7566. E-mail: daniela.debiase{at}uniroma1.it.

{triangledown} Published ahead of print on 15 September 2006.

Journal of Bacteriology, December 2006, p. 8118-8127, Vol. 188, No. 23
0021-9193/06/$08.00+0     doi:10.1128/JB.01044-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Hu, Y., Lu, P., Wang, Y., Ding, L., Atkinson, S., Chen, S. (2009). OmpR positively regulates urease expression to enhance acid survival of Yersinia pseudotuberculosis. Microbiology 155: 2522-2531 [Abstract] [Full Text]  
  • Kailasan Vanaja, S., Bergholz, T. M., Whittam, T. S. (2009). Characterization of the Escherichia coli O157:H7 Sakai GadE Regulon. J. Bacteriol. 191: 1868-1877 [Abstract] [Full Text]  
  • Sadykov, M. R., Olson, M. E., Halouska, S., Zhu, Y., Fey, P. D., Powers, R., Somerville, G. A. (2008). Tricarboxylic Acid Cycle-Dependent Regulation of Staphylococcus epidermidis Polysaccharide Intercellular Adhesin Synthesis. J. Bacteriol. 190: 7621-7632 [Abstract] [Full Text]  
  • Stoebel, D. M., Free, A., Dorman, C. J. (2008). Anti-silencing: overcoming H-NS-mediated repression of transcription in Gram-negative enteric bacteria. Microbiology 154: 2533-2545 [Abstract] [Full Text]  
  • Gualdi, L., Tagliabue, L., Landini, P. (2007). Biofilm Formation-Gene Expression Relay System in Escherichia coli: Modulation of {sigma}S-Dependent Gene Expression by the CsgD Regulatory Protein via {sigma}S Protein Stabilization. J. Bacteriol. 189: 8034-8043 [Abstract] [Full Text]  
  • Bergholz, T. M., Tarr, C. L., Christensen, L. M., Betting, D. J., Whittam, T. S. (2007). Recent Gene Conversions between Duplicated Glutamate Decarboxylase Genes (gadA and gadB) in Pathogenic Escherichia coli. Mol Biol Evol 24: 2323-2333 [Abstract] [Full Text]  
  • Richard, H., Foster, J. W. (2007). Sodium regulates Escherichia coli acid resistance, and influences GadX- and GadW-dependent activation of gadE. Microbiology 153: 3154-3161 [Abstract] [Full Text]  
  • Sayed, A. K., Odom, C., Foster, J. W. (2007). The Escherichia coli AraC-family regulators GadX and GadW activate gadE, the central activator of glutamate-dependent acid resistance. Microbiology 153: 2584-2592 [Abstract] [Full Text]  
  • Mates, A. K., Sayed, A. K., Foster, J. W. (2007). Products of the Escherichia coli Acid Fitness Island Attenuate Metabolite Stress at Extremely Low pH and Mediate a Cell Density-Dependent Acid Resistance. J. Bacteriol. 189: 2759-2768 [Abstract] [Full Text]  


Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»