Iron acquisition by group B streptococcus

2006-01-20 12:01:07 AM
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These data provide the first evidence of siderophore-mediated iron
acquisition by GBS
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Mol Microbiol. 2006 Jan;59(2):707-21. Related Articles, Links
Evidence for siderophore-dependent iron acquisition in group B
streptococcus.
Clancy A, Loar JW, Speziali CD, Oberg M, Heinrichs DE, Rubens CE.
Division of Infectious Diseases, Immunology, and Rheumatology,
Department of Pediatrics, Children's Hospital and Regional Medical
Center/University of Washington, 307 Westlake Avenue N, Seattle WA
98109, USA.
Mutagenesis of group B streptococcus (GBS) with TnphoZ, a transposon
designed to identify secreted protein genes, identified the gene
homologues fhuD and fhuG. The encoded proteins participate in
siderophore (hydroxamate)-dependent iron(III) transport in other
bacterial species. Sequence analysis of the genome determined that fhuD
and fhuG are members of a polycistronic operon comprised of four genes,
fhuCDBG, that encode a putative ATPase, cell surface receptor and two
transmembrane proteins respectively. We hypothesized that FhuD was a
siderophore receptor. Western analysis of cell extracts localized FhuD
to the bacterial cell membrane. Fluorescence quenching experiments
determined that purified FhuD bound hydroxamate-type siderophores. FhuD
displayed highest affinity for iron(III)-desferroxamine, with a K(D)
(microM) = 0.05, identical to that described for FhuD2 from
Staphylococcus aureus. The role of Fhu in siderophore-iron transport
was also characterized. A fhu mutant, ACFhu1, was equally sensitive to
the iron-dependent antibiotic streptonigrin as the wild-type strain,
suggesting that ACFhu1 was not reduced for intracellular iron
concentrations in the absence of exogenous siderophore. However, ACFhu1
transported significantly less siderophore-bound iron in (55)Fe
accumulation assays. These data provide the first evidence of
siderophore-mediated iron acquisition by GBS.
PMID: 16390461 [PubMed - in process]
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