Determination of ferrichrome binding to the FhuA outer membrane transport protein, periplasmic accumulation of ferrichrome, or transport of ferrichrome into cells using a three-layer oil technique

Killmann, Helmut; Gestwa, Glikeria

doi:10.1016/s0003-2697(02)00285-3

Cited by 2 publications

(1 citation statement)

References 13 publications

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“…The calculated dissociation constant (Kd) of PiaA towards ferrichrome is 5.8±1.4 nM, which is about 1/20 to that of E. coli FhuD towards ferrichrome (Kd = 0.1 µM) [33]. This much higher affinity enables the Gram-positive bacteria S. pneumoniae to bind the substrates at a rather lower concentration in the environment, whereas FhuD does not require such a high affinity because the substrates have been readily enriched in the periplasmic space in E. coli [34].…”

Section: Resultsmentioning

confidence: 96%

Structures of Streptococcus pneumoniae PiaA and Its Complex with Ferrichrome Reveal Insights into the Substrate Binding and Release of High Affinity Iron Transporters

Wang

Jiang

et al. 2013

PLoS ONE

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Iron scarcity is one of the nutrition limitations that the Gram-positive infectious pathogens Streptococcus pneumoniae encounter in the human host. To guarantee sufficient iron supply, the ATP binding cassette (ABC) transporter Pia is employed to uptake iron chelated by hydroxamate siderophore, via the membrane-anchored substrate-binding protein PiaA. The high affinity towards ferrichrome enables PiaA to capture iron at a very low concentration in the host. We presented here the crystal structures of PiaA in both apo and ferrichrome-complexed forms at 2.7 and 2.1 Å resolution, respectively. Similar to other class III substrate binding proteins, PiaA is composed of an N-terminal and a C-terminal domain bridged by an α-helix. At the inter-domain cleft, a molecule of ferrichrome is stabilized by a number of highly conserved residues. Upon ferrichrome binding, two highly flexible segments at the entrance of the cleft undergo significant conformational changes, indicating their contribution to the binding and/or release of ferrichrome. Superposition to the structure of Escherichia coli ABC transporter BtuF enabled us to define two conserved residues: Glu119 and Glu262, which were proposed to form salt bridges with two arginines of the permease subunits. Further structure-based sequence alignment revealed that the ferrichrome binding pattern is highly conserved in a series of PiaA homologs encoded by both Gram-positive and negative bacteria, which were predicted to be sensitive to albomycin, a sideromycin antibiotic derived from ferrichrome.

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Section: Resultsmentioning

confidence: 96%

Structures of Streptococcus pneumoniae PiaA and Its Complex with Ferrichrome Reveal Insights into the Substrate Binding and Release of High Affinity Iron Transporters

Wang

Jiang

et al. 2013

PLoS ONE

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Loop Deletions Indicate Regions Important for FhuA Transport and Receptor Functions in Escherichia coli

Endriss

Braun

2004

J Bacteriol

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Precise deletions of cell surface-exposed loops of FhuA resulted in mutants of Escherichia coli with distinct phenotypes. Deletion of loop 3 or 11 inactivated ferrichrome transport activity. Deletion of loop 8 inactivated receptor activity for colicin M and the phages T1, T5, and 80. The loop 7 deletion mutant was colicin M resistant but fully phage sensitive. The loop 4 deletion mutant was resistant to the TonB-dependent phages T1 and 80 but fully sensitive to the TonB-independent phage T5. The phenotypes of the deletion mutants revealed important sites for the multiple FhuA transport and receptor activities. The ligand binding sites are nonidentical and are distributed among the entire exposed surface. Presumably, FhuA evolved as a ferrichrome transporter and was subsequently used as a receptor by the phages and colicin M, which selected the same as well as distinct loops as receptor sites.

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Determination of ferrichrome binding to the FhuA outer membrane transport protein, periplasmic accumulation of ferrichrome, or transport of ferrichrome into cells using a three-layer oil technique

Cited by 2 publications

References 13 publications

Structures of Streptococcus pneumoniae PiaA and Its Complex with Ferrichrome Reveal Insights into the Substrate Binding and Release of High Affinity Iron Transporters

Structures of Streptococcus pneumoniae PiaA and Its Complex with Ferrichrome Reveal Insights into the Substrate Binding and Release of High Affinity Iron Transporters

Loop Deletions Indicate Regions Important for FhuA Transport and Receptor Functions in Escherichia coli

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