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Journal of Bacteriology, September 2001, p. 4994-5000, Vol. 183, No. 17
Department of Microbiology and Immunology,
University of Western Ontario, London, Ontario, Canada
Received 6 April 2001/Accepted 15 June 2001
Staphylococcus aureus can utilize several hydroxamate
siderophores for growth under iron-restricted conditions. Previous
findings have shown that S. aureus possesses a cytoplasmic
membrane-associated traffic ATPase that is involved in the specific
transport of iron(III)-hydroxamate complexes. In this study, we have
identified two additional genes, termed fhuD1 and
fhuD2, whose products are involved in this transport process in S. aureus. We have shown that fhuD2
codes for a posttranslationally modified lipoprotein that is anchored
in the cytoplasmic membrane, while the deduced amino acid sequence
predicts the same for fhuD1. The predicted FhuD1 and FhuD2
proteins share 41.0% identity and 56.4% total similarity with each
other, 45.9 and 49.1% total similarity with the FhuD homolog in
Bacillus subtilis, and 29.3 and 24.6% total similarity
with the periplasmic FhuD protein from Escherichia coli.
Insertional inactivation and gene replacement of both genes showed that
while FhuD2 is involved in the transport of iron(III) in complex with
ferrichrome, ferrioxamine B, aerobactin, and coprogen, FhuD1 shows a
more limited substrate range, capable of only iron(III)-ferrichrome and
iron(III)-ferrioxamine B transport in S. aureus. Nucleotide sequences present upstream of both fhuD1 and
fhuD2 predict the presence of consensus Fur binding
sequences. In agreement, transcription of both genes was negatively
regulated by exogenous iron levels through the activity of the S. aureus Fur protein.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.17.4994-5000.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Identification and Characterization of
fhuD1 and fhuD2, Two Genes Involved in
Iron-Hydroxamate Uptake 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}uwo.ca.
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