Yersinia pestis TonB: Role in Iron, Heme, and Hemoprotein Utilization

ABSTRACT In Yersinia pestis, the siderophore-dependent yersiniabactin (Ybt) iron transport system and heme transport system (Hmu) have putative TonB-dependent outer membrane receptors. Here we demonstrate that hemin uptake and iron utilization from Ybt are TonB dependent. However, the Yfe iron and manganese transport system does not require TonB.

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ShmR Is Essential for Utilization of Heme as a Nutritional Iron Source in Sinorhizobium meliloti

Applied and Environmental Microbiology ◽

10.1128/aem.01590-08 ◽

2008 ◽

Vol 74 (20) ◽

pp. 6473-6475 ◽

Cited By ~ 8

Author(s):

Vanesa Amarelle ◽

Mark R. O'Brian ◽

Elena Fabiano

Keyword(s):

Membrane Protein ◽

Outer Membrane ◽

Transport System ◽

Outer Membrane Protein ◽

Sinorhizobium Meliloti ◽

Receptor Protein ◽

Iron Source ◽

Heme Transport

ABSTRACT The bacterium Sinorhizobium meliloti is able to use heme as a nutritional iron source. Here, we show that the iron-regulated shmR gene encodes an outer membrane protein required for growth on heme. Furthermore, an shmR mutant is resistant to the toxic heme analog gallium protoporphyrin. Thus, the receptor protein of the heme transport system has been identified in S. meliloti.

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Free and Hemophore-Bound Heme Acquisitions through the Outer Membrane Receptor HasR Have Different Requirements for the TonB-ExbB-ExbD Complex

Journal of Bacteriology ◽

10.1128/jb.186.13.4067-4074.2004 ◽

2004 ◽

Vol 186 (13) ◽

pp. 4067-4074 ◽

Cited By ~ 56

Author(s):

Sylvie Létoffé ◽

Philippe Delepelaire ◽

Cécile Wandersman

Keyword(s):

Outer Membrane ◽

Energy Requirement ◽

Membrane Receptor ◽

Membrane Receptors ◽

Gram Negative Bacteria ◽

Outer Membrane Receptor ◽

Heme Uptake ◽

Heme Transport ◽

Carbonyl Cyanide ◽

Free Heme

ABSTRACT Many gram-negative bacteria have specific outer membrane receptors for free heme, hemoproteins, and hemophores. Heme is a major iron source and is taken up intact, whereas hemoproteins and hemophores are not transported: the iron-containing molecule has to be stripped off at the cell surface, with only the heme moiety being taken up. The Serratia marcescens hemophore-specific outer membrane receptor HasR can transport either heme itself or heme bound to the hemophore HasA. This second mechanism is much more efficient and requires a higher TonB-ExbB-ExbD (TonB complex) concentration than does free or hemoglobin-bound heme uptake. This requirement for more of the TonB complex is associated with a higher energy requirement. Indeed, the sensitivity of heme-hemophore uptake to the protonophore carbonyl cyanide m-chlorophenyl hydrazone is higher than that of heme uptake from hemoglobin. We show that a higher TonB complex concentration is required for hemophore dissociation from the receptor. This dissociation is concomitant with heme uptake. We propose that increasing the TonB complex concentration drives more energy to the outer membrane receptor and speeds up the release of empty hemophores, which, if they remained on receptors, would inhibit heme transport.

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Iron transport and signal transduction inPseudomonas aeruginosa: crystal structures of the TonB-dependent outer membrane receptors FpvA and FptA

Acta Crystallographica Section A Foundations of Crystallography ◽

10.1107/s0108767306099399 ◽

2006 ◽

Vol 62 (a1) ◽

pp. s30-s30

Author(s):

C. Wirth ◽

H. Celia ◽

F. Pattus ◽

D. Cobessi

Keyword(s):

Signal Transduction ◽

Outer Membrane ◽

Crystal Structures ◽

Iron Transport ◽

Membrane Receptors

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Engineering Rhizobial Bioinoculants: A Strategy to Improve Iron Nutrition

The Scientific World JOURNAL ◽

10.1155/2013/315890 ◽

2013 ◽

Vol 2013 ◽

pp. 1-15 ◽

Cited By ~ 8

Author(s):

S. J. Geetha ◽

Sanket J. Joshi

Keyword(s):

Genetic Engineering ◽

Plant Growth ◽

Outer Membrane ◽

Iron Transport ◽

Iron Acquisition ◽

Membrane Receptors ◽

Iron Nutrition ◽

Nodule Occupancy ◽

Rhizobial Strain ◽

Hydroxamate Siderophores

Under field conditions, inoculated rhizobial strains are at a survival disadvantage as compared to indigenous strains. In order to out-compete native rhizobia it is not only important to develop strong nodulation efficiency but also increase their competence in the soil and rhizosphere. Competitive survival of the inoculated strain may be improved by employing strain selection and by genetic engineering of superior nitrogen fixing strains. Iron sufficiency is an important factor determining the survival and nodulation by rhizobia in soil. Siderophores, a class of ferric specific ligands that are involved in receptor specific iron transport into bacteria, constitute an important part of iron acquisition systems in rhizobia and have been shown to play a role in symbiosis as well as in saprophytic survival. Soils predominantly have iron bound to hydroxamate siderophores, a pool that is largely unavailable to catecholate-utilizing rhizobia. Outer membrane receptors for uptake of ferric hydroxamates include FhuA and FegA which are specific for ferrichrome siderophore. Increase in nodule occupancy and enhanced plant growth of thefegAandfhuAexpressing engineered bioinoculants rhizobial strain have been reported. Engineering rhizobia for developing effective bioinoculants with improved ability to utilize heterologous siderophores could provide them with better iron acquisition ability and consequently, rhizospheric stability.

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