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Journal of Bacteriology, March 2008, p. 1866-1870, Vol. 190, No. 6
0021-9193/08/$08.00+0 doi:10.1128/JB.01636-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Unité des Membranes Bactériennes, Département de Microbiologie, Institut Pasteur, CNRS URA 2172, 75724 Paris Cedex 15, France
Received 9 October 2007/ Accepted 23 December 2007
Serratia marcescens hemTUV genes encoding a potential heme permease were cloned in Escherichia coli recombinant mutant FB827 dppF::Km(pAM 238-hasR). This strain, which expresses HasR, a foreign heme outer membrane receptor, is potentially capable of using heme as an iron source. However, this process is invalidated due to a dppF::Km mutation which inactivates the Dpp heme/peptide permease responsible for heme, dipeptide, and
-aminolevulinic (ALA) transport through the E. coli inner membrane. We show here that hemTUV genes complement the Dpp permease for heme utilization as an iron source and thus are functional in E. coli. However, hemTUV genes do not complement the Dpp permease for ALA uptake, indicating that the HemTUV permease does not transport ALA. Peptides do not inhibit heme uptake in vivo, indicating that, unlike Dpp permease, HemTUV permease does not transport peptides. HemT, the periplasmic binding protein, binds heme. Heme binding is saturable and not inhibited by peptides that inhibit heme uptake by the Dpp system. Thus, the S. marcescens HemTUV permease and, most likely, HemTUV orthologs present in many gram-negative pathogens form a class of heme-specific permeases different from the Dpp peptide/heme permease characterized in E. coli.
Published ahead of print on 4 January 2008.
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