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Journal of Bacteriology, February 2005, p. 980-990, Vol. 187, No. 3
0021-9193/05/$08.00+0     doi:10.1128/JB.187.3.980-990.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Functional Interactions between the Carbon and Iron Utilization Regulators, Crp and Fur, in Escherichia coli

Zhongge Zhang,1 Guillermo Gosset,1,2 Ravi Barabote,1 Claudio S. Gonzalez,1 William A. Cuevas,3 and Milton H. Saier Jr.1*

Division of Biological Sciences, University of California at San Diego, La Jolla,1 Genencor International, Inc., Palo Alto, California,3 Departamento de Ingenieria Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, México2

Received 26 July 2004/ Accepted 26 October 2004

In Escherichia coli, the ferric uptake regulator (Fur) controls expression of the iron regulon in response to iron availability while the cyclic AMP receptor protein (Crp) regulates expression of the carbon regulon in response to carbon availability. We here identify genes subject to significant changes in expression level in response to the loss of both Fur and Crp. Many iron transport genes and several carbon metabolic genes are subject to dual control, being repressed by the loss of Crp and activated by the loss of Fur. However, the sodB gene, encoding superoxide dismutase, and the aceBAK operon, encoding the glyoxalate shunt enzymes, show the opposite responses, being activated by the loss of Crp and repressed by the loss of Fur. Several other genes including the sdhA-D, sucA-D, and fumA genes, encoding key constituents of the Krebs cycle, proved to be repressed by the loss of both transcription factors. Finally, the loss of both Crp and Fur activated a heterogeneous group of genes under {sigma}S control encoding, for example, the cyclopropane fatty acid synthase, Cfa, the glycogen synthesis protein, GlgS, the 30S ribosomal protein, S22, and the mechanosensitive channel protein, YggB. Many genes appeared to be regulated by the two transcription factors in an apparently additive fashion, but apparent positive or negative cooperativity characterized several putative Crp/Fur interactions. Relevant published data were evaluated, putative Crp and Fur binding sites were identified, and representative results were confirmed by real-time PCR. Molecular explanations for some, but not all, of these effects are provided.


* Corresponding author. Mailing address: Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116. Phone: (858) 534-4084. Fax: (858) 534-7108. E-mail: msaier{at}ucsd.edu.


Journal of Bacteriology, February 2005, p. 980-990, Vol. 187, No. 3
0021-9193/05/$08.00+0     doi:10.1128/JB.187.3.980-990.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.




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