Previous Article | Next Article 
Journal of Bacteriology, March 2002, p. 1407-1416, Vol. 184, No. 5
0021-9193/02/$04.00+0 DOI: 10.1128/JB.184.5.1407-1416.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Posttranscriptional Activation of the Transcriptional Activator Rob by Dipyridyl in Escherichia coli
***
Judah L. Rosner,1* Bindi Dangi,2 Angela M. Gronenborn,2 and Robert G. Martin1
Laboratory of Molecular Biology,1
Laboratory of Chemical Physics, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-05602
Received 5 October 2001/
Accepted 28 November 2001
The transcriptional activator Rob consists of an N-terminal domain (NTD) of 120 amino acids responsible for DNA binding and promoter activation and a C-terminal domain (CTD) of 169 amino acids of unknown function. Although several thousand molecules of Rob are normally present per Escherichia coli cell, they activate promoters of the rob regulon poorly. We report here that in cells treated with either 2,2"- or 4,4"-dipyridyl (the latter is not a metal chelator), Rob-mediated transcription of various rob regulon promoters was increased substantially. A small, growth-phase-dependent effect of dipyridyl on the rob promoter was observed. However, dipyridyl enhanced Rob's activity even when rob was regulated by a heterologous (lac) promoter showing that the action of dipyridyl is mainly posttranscriptional. Mutants lacking from 30 to 166 of the C-terminal amino acids of Rob had basal levels of activity similar to that of wild-type cells, but dipyridyl treatment did not enhance this activity. Thus, the CTD is not an inhibitor of Rob but is required for activation of Rob by dipyridyl. In contrast to its relatively low activity in vivo, Rob binding to cognate DNA and activation of transcription in vitro is similar to that of MarA, which has a homologous NTD but no CTD. In vitro nuclear magnetic resonance studies demonstrated that 2,2"-dipyridyl binds to Rob but not to the CTD-truncated Rob or to MarA, suggesting that the effect of dipyridyl on Rob is direct. Thus, it appears that Rob can be converted from a low activity state to a high-activity state by a CTD-mediated mechanism in vivo or by purification in vitro.
* Corresponding author. Mailing address: Laboratory of Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, NIH, Bldg. 5, Rm. 333, Bethesda, MD 20892-0560. Phone: (301) 496-5466. Fax: (301) 496-0201. E-mail:
jlrosner{at}helix.nih.gov.
Journal of Bacteriology, March 2002, p. 1407-1416, Vol. 184, No. 5
0021-9193/02/$04.00+0 DOI: 10.1128/JB.184.5.1407-1416.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
This article has been cited by other articles:
-
Rosner, J. L., Martin, R. G.
(2009). An Excretory Function for the Escherichia coli Outer Membrane Pore TolC: Upregulation of marA and soxS Transcription and Rob Activity Due to Metabolites Accumulated in tolC Mutants. J. Bacteriol.
191: 5283-5292
[Abstract]
[Full Text]
-
Barchiesi, J., Castelli, M. E., Soncini, F. C., Vescovi, E. G.
(2008). mgtA Expression Is Induced by Rob Overexpression and Mediates a Salmonella enterica Resistance Phenotype. J. Bacteriol.
190: 4951-4958
[Abstract]
[Full Text]
-
Dupont, M., James, C. E., Chevalier, J., Pages, J.-M.
(2007). An Early Response to Environmental Stress Involves Regulation of OmpX and OmpF, Two Enterobacterial Outer Membrane Pore-Forming Proteins. Antimicrob. Agents Chemother.
51: 3190-3198
[Abstract]
[Full Text]
-
Schneiders, T., Levy, S. B.
(2006). MarA-mediated Transcriptional Repression of the rob Promoter. J. Biol. Chem.
281: 10049-10055
[Abstract]
[Full Text]
-
Madsen, M. L., Nettleton, D., Thacker, E. L., Minion, F. C.
(2006). Transcriptional profiling of Mycoplasma hyopneumoniae during iron depletion using microarrays.. Microbiology
152: 937-944
[Abstract]
[Full Text]
-
Nikaido, H.
(2003). Molecular Basis of Bacterial Outer Membrane Permeability Revisited. Microbiol. Mol. Biol. Rev.
67: 593-656
[Abstract]
[Full Text]
-
Garrido, M. E., Bosch, M., Medina, R., Bigas, A., Llagostera, M., Perez de Rozas, A. M., Badiola, I., Barbe, J.
(2003). fur-independent regulation of the Pasteurella multocida hbpA gene encoding a haemin-binding protein. Microbiology
149: 2273-2281
[Abstract]
[Full Text]
-
Grkovic, S., Brown, M. H., Skurray, R. A.
(2002). Regulation of Bacterial Drug Export Systems. Microbiol. Mol. Biol. Rev.
66: 671-701
[Abstract]
[Full Text]
-
Godsey, M. H., Zheleznova Heldwein, E. E., Brennan, R. G.
(2002). Structural Biology of Bacterial Multidrug Resistance Gene Regulators. J. Biol. Chem.
277: 40169-40172
[Full Text]
-
Michan, C., Manchado, M., Pueyo, C.
(2002). SoxRS Down-Regulation of rob Transcription. J. Bacteriol.
184: 4733-4738
[Abstract]
[Full Text]