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Journal of Bacteriology, August 2008, p. 5224-5229, Vol. 190, No. 15
0021-9193/08/$08.00+0     doi:10.1128/JB.01782-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Lysine Represses Transcription of the Escherichia coli dapB Gene by Preventing Its Activation by the ArgP Activator{triangledown} ,{dagger}

Jean Bouvier,1,2 Patrick Stragier,3 Violette Morales,1,2 Elisabeth Rémy,1,2,{ddagger} and Claude Gutierrez1,2*

Université Paul Sabatier Toulouse III, Laboratoire de Microbiologie et Génétique Moléculaire, F31000 Toulouse, France,1 Centre National de la Recherche Scientifique, Laboratoire de Microbiologie et Génétique Moléculaire, F31000 Toulouse, France,2 Centre National de la Recherche Scientifique, Institut de Biologie Physico-Chimique, F75000 Paris, France3

Received 11 November 2007/ Accepted 6 May 2008

The Escherichia coli dapB gene encodes one of the enzymes of the biosynthetic pathway leading to lysine and its immediate precursor, diaminopimelate. Expression of dapB is repressed by lysine, but no trans-acting regulator has been identified so far. Our analysis of the dapB regulatory region shows that sequences located in the –81/–118 interval upstream of the transcription start site are essential for full expression of dapB, as well as for lysine repression. Screening a genomic library for a gene that could alleviate lysine repression when present in multicopy led to the recovery of argP, a gene encoding an activating protein of the LysR-type family, known to use lysine as an effector. An argP null mutation strongly decreases dapB transcription that becomes insensitive to lysine. Purified His6-tagged ArgP protein binds with an apparent Kd of 35 nM to the dapB promoter in a gel retardation assay, provided that sequences up to –103 are present. In the presence of L-lysine and L-arginine, the binding of ArgP to dapB is partly relieved. These results fit with a model in which ArgP contributes to enhanced transcription of dapB when lysine becomes limiting.

* Corresponding author. Mailing address: Université Paul Sabatier-CNRS, LMGM, Bât. IBCG, 118 route de Narbonne, F31062 Toulouse Cedex 9, France. Phone: (33) 561 33 59 72. Fax: (33) 561 33 58 86. E-mail: Claude.Gutierrez{at}ibcg.biotoul.fr

{triangledown} Published ahead of print on 23 May 2008.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

{ddagger} Present address: Sanofi-Aventis R&D, 94403 Vitry sur Seine, France.

Journal of Bacteriology, August 2008, p. 5224-5229, Vol. 190, No. 15
0021-9193/08/$08.00+0     doi:10.1128/JB.01782-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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