The Escherichia coli K-12 NarL and NarP Proteins Insulate the nrf Promoter from the Effects of Integration Host Factor

Author:

Browning Douglas F.1,Lee David J.1,Wolfe Alan J.2,Cole Jeffrey A.1,Busby Stephen J. W.1

Affiliation:

1. School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom

2. Department of Microbiology and Immunology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois 60153

Abstract

ABSTRACT The Escherichia coli K-12 nrf operon promoter can be activated fully by the FNR protein (regulator of fumarate and nitrate reduction) binding to a site centered at position −41.5. FNR-dependent transcription is suppressed by integration host factor (IHF) binding at position −54, and this suppression is counteracted by binding of the NarL or NarP response regulator at position −74.5. The E. coli acs gene is transcribed from a divergent promoter upstream from the nrf operon promoter. Transcription from the major acs P2 promoter is dependent on the cyclic AMP receptor protein and is modulated by IHF and Fis binding at multiple sites. We show that IHF binding to one of these sites, located at position −127 with respect to the nrf promoter, has a positive effect on nrf promoter activity. This activation is dependent on the face of the DNA helix, independent of IHF binding at other locations, and found only when NarL/NarP are not bound at position −74.5. Binding of NarL/NarP appears to insulate the nrf promoter from the effects of IHF. The acs-nrf regulatory region is conserved in other pathogenic E. coli strains and related enteric bacteria but differs in Salmonella enterica serovar Typhimurium.

Publisher

American Society for Microbiology

Subject

Molecular Biology,Microbiology

Reference26 articles.

1. Cyclic AMP Receptor Protein-Dependent Activation of the Escherichia coli acs P2 Promoter by a Synergistic Class III Mechanism

2. Browning, D., D. Lee, J. Green, and S. J. W. Busby. 2002. Secrets of bacterial transcription initiation taught by the Escherichia coli FNR protein, p. 127-142. In D. A. Hodgson and C. M. Thomas (ed.), Signals, switches, regulons, and cascades. Cambridge University Press, Cambridge, United Kingdom.

3. Browning, D. F., C. M. Beatty, A. J. Wolfe, J. A. Cole, and S. J. W. Busby. 2002. Independent regulation of the divergent Escherichia coli nrfA and acsP1 promoters by a nucleoprotein assembly at a shared regulatory region. Mol. Microbiol. 43 : 687-701.

4. Browning, D. F., C. M. Beatty, E. A. Sanstad, K. A. Gunn, S. J. W. Busby, and A. J. Wolfe. 2004. Modulation of CRP-dependent transcription at the Escherichia coli acsP2 promoter by nucleoprotein complexes: anti-activation by the nucleoid proteins FIS and IHF. Mol. Microbiol. 51 : 241-254.

5. Browning, D. F., J. A. Cole, and S. J. W. Busby. 2004. Transcription activation by remodelling of a nucleoprotein assembly: the role of NarL at the FNR-dependent Escherichia coli nir promoter. Mol. Microbiol. 53 : 203-215.

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