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Infect. Immun. doi:10.1128/IAI.00866-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Identification and Characterization of a Novel ABC Iron Transport System, fit, in Escherichia coli

Department of Veterinary and Biomedical Sciences, University of Minnesota, 1971 Commonwealth Ave, ST PAUL, MN 55108

^* To whom correspondence should be addressed. Email: isaac015{at}umn.edu.

	Abstract

A putative ABC transporter, fit, with significant homology to several bacterial iron transporters, was identified in Escherichia coli. The E. coli fit system consists of 6 genes designated fitA, -B, -C, -D, -E and fitR. Based on DNA sequence analysis, fit encodes an outer membrane protein (FitA), a periplasmic binding protein (FitE), two permease proteins (FitC and -D), an ATPase (FitB), and a hypothetical protein (FitR). Introduction of the E. coli fit system into an E. coli K12 strain increased intracellular iron content and transformed bacteria were more sensitive to streptonigrin, which suggested that fit transports iron in E. coli. Expression of fit was studied using a lacZ reporter assay. A functional, bidirectional promoter was identified in the intergenic region between gene fitA and fitB. The expression of the E. coli fit system was found to be induced by iron limitation, and repressed when Fe²⁺ was added to minimal media. Several fit mutants were created in E. coli using an in vitro transposon mutagenesis strategy. Mutations in fit did not affect bacterial growth in iron-restricted media. Using a growth promotion test, it was found that fit was not able to transport enterobactin, ferrichrome, transferrin, and lactoferrin in E. coli.

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