Identification of a Novel Regulator for the Escherichia coli fit Iron Transport System

Zhiming Ouyang1, Richard Isaacson*
1 Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas USA
* Department of Veterinary and Biomedical Science, University of Minnesota, ST PAUL, MN, USA

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© Ouyang and Isaacson; Licensee Bentham Open.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestrictive use, distribution, and reproduction in any medium, provided the original work is properly cited.

* Address correspondence to this author at the Department of Veterinary and Biomedical Science, University of Minnesota, ST PAUL, MN, USA; Tel: (612) 624-0701; Fax: (612) 625-5203; E-mail:


The Escherichia coli fit iron transport system consists of 6 genes, fitA, B, C, D, E and fitR. Based on in silico analysis, FitA-E composes a typical bacterial iron transporter, while FitR was deduced to be a regulator. In this paper the regulation of fit expression by FitR was studied using a quantitative RT-PCR technique and a lacZ reporter assay. It was found that fit expression was repressed when FitR was over-expressed and de-repressed when fitR was knocked out by mutation. When the mutation in fitR was complemented in trans- with the wild type fitR gene, repression of fit expression by FitR was restored. Finally, recombinant FitR was found to bind to the fit promoter DNA when employed in an electrophoretic mobility-shift assay. These results demonstrated that fitR encodes an auto-repressor for the E. colifit system.