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Journal of Bacteriology, August 2000, p. 4394-4400, Vol. 182, No. 16
Department of Microbiology and Immunology,
University of Western Ontario, London, Ontario, Canada, N6A 5C1
Received 4 April 2000/Accepted 19 May 2000
Staphylococcus aureus was shown to transport iron
complexed to a variety of hydroxamate type siderophores, including
ferrichrome, aerobactin, and desferrioxamine. An S. aureus
mutant defective in the ability to transport ferric hydroxamate
complexes was isolated from a Tn917-LTV1 transposon
insertion library after selection on iron-limited media containing
aerobactin and streptonigrin. Chromosomal DNA flanking the
Tn917-LTV1 insertion was identified by sequencing of
chromosomal DNA isolated from the mutant. This information localized
the transposon insertion to a gene whose predicted product shares
significant similarity with FhuG of Bacillus subtilis. DNA
sequence information was then used to clone a larger fragment of DNA
surrounding the fhuG gene, and this resulted in the
identification of an operon of three genes, fhuCBG, all of which show significant similarities to ferric hydroxamate uptake (fhu) genes in B. subtilis. FhuB and FhuG are
highly hydrophobic, suggesting that they are embedded within the
cytoplasmic membrane, while FhuC shares significant homology with
ATP-binding proteins. Given this, the S. aureus FhuCBG
proteins were predicted to be part of a binding protein-dependent
transport system for ferric hydroxamates. Exogenous iron levels were
shown to regulate ferric hydroxamate uptake in S. aureus.
This regulation is attributable to Fur in S. aureus because
a strain containing an insertionally inactivated fur gene
showed maximal levels of ferric hydroxamate uptake even when the cells
were grown under iron-replete conditions. By using the Fur titration
assay, it was shown that the Fur box sequences upstream of
fhuCBG are recognized by the Escherichia coli
Fur protein.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Identification and Characterization of a Membrane Permease
Involved in Iron-Hydroxamate Transport in
Staphylococcus aureus
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, University of Western Ontario, London,
Ontario, Canada N6A 5C1. Phone: 519 661 3984. Fax: 519 661 3499. E-mail: deh{at}julian.uwo.ca.
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