scholarly journals The Hem and Has haem uptake systems in Serratia marcescens

Microbiology ◽  
2010 ◽  
Vol 156 (6) ◽  
pp. 1749-1757 ◽  
Author(s):  
Najla Benevides-Matos ◽  
Francis Biville
Keyword(s):  
Serratia Marcescens ◽  
Outer Membrane ◽  
Membrane Receptor ◽  
Gram Negative Bacteria ◽  
Uptake System ◽  
Outer Membrane Receptor ◽  
Iron Depletion ◽  
Two Systems ◽  
Uptake Activity ◽  
Different Sources

Serratia marcescens, like several other Gram-negative bacteria, possesses two functional haem uptake systems. The first, referred to as the Hem system, can transport haem present at a concentration equal to or above 10−6 M. It requires an active outer-membrane receptor which uses proton-motive force energy transmitted by the inner-membrane TonB protein. The other system, Has, takes up haem at lower concentrations and utilizes a small secreted haem-binding protein (haemophore) and its cognate TonB-dependent outer-membrane receptor HasR. Various combinations of mutations were used to examine haem uptake activity by the two systems in S. marcescens. The Hem uptake system enables S. marcescens to take up haem at a concentration of 10−6 M in the presence of various levels of iron depletion. The Has system, which enables such uptake even in the presence of lower haem concentrations, requires higher iron depletion conditions for function. Has haem uptake requires the presence of HasB, a TonB paralogue encoded by the has operon. These two systems enable S. marcescens to take up haem under various conditions from different sources, reflecting its capacity to confront conditions encountered in natural biotopes.

A new mechanism for membrane iron transport in Pseudomonas aeruginosa

2002 ◽  
Vol 30 (4) ◽  
pp. 702-705 ◽  
Author(s):  
I.J. Schalk ◽  
M. A. Abdallah ◽  
F. Pattus
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Outer Membrane ◽  
Iron Uptake ◽  
Iron Transport ◽  
Membrane Receptor ◽  
Gram Negative Bacteria ◽  
Outer Membrane Receptor ◽  
Uptake Mechanism ◽  
Atp Binding Cassette Transporter ◽  
Biophysical Studies

Various biochemical and biophysical studies have demonstrated the existence of a novel iron-uptake mechanism in Pseudomonas aeruginosa, different from that generally described for ferrichrome and ferric-enterobactin in Escherichia coli. This new iron-uptake mechanism involves all the proteins generally reported to be involved in the uptake of ferric-siderophore complexes in Gram-negative bacteria (i.e. the outer membrane receptor, periplasmic binding protein and ATP-binding-cassette transporter), but differs in the behaviour of the siderophore. One of the key features of this process is the binding of iron-free pyoverdin to the outer membrane receptor FpvA in conditions of iron deficiency.

scholarly journals Contributions of the heme coordinating ligands of the Pseudomonas aeruginosa outer membrane receptor HasR to extracellular heme sensing and transport

2020 ◽  
Vol 295 (30) ◽  
pp. 10456-10467 ◽  
Author(s):  
Alecia T. Dent ◽  
Angela Wilks
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Outer Membrane ◽  
Membrane Receptor ◽  
Site Directed Mutagenesis ◽  
Uptake System ◽  
Outer Membrane Receptor ◽  
Heme Uptake ◽  
Functional Link ◽  
Heme Transport ◽  
Σ Factor

Pseudomonas aeruginosa exhibits a high requirement for iron, which it can acquire via several mechanisms, including the acquisition and utilization of heme. The P. aeruginosa genome encodes two heme uptake systems, the heme assimilation system (Has) and the Pseudomonas heme utilization (Phu) system. Extracellular heme is sensed via the Has system, which encodes an extracytoplasmic function (ECF) σ factor system. Previous studies have shown that the transfer of heme from the extracellular hemophore HasAp to the outer membrane receptor HasR is required for activation of the σ factor HasI and upregulation of has operon expression. Here, employing site-directed mutagenesis, allelic exchange, quantitative PCR analyses, immunoblotting, and 13C-heme uptake experiments, we delineated the differential contributions of the extracellular FRAP/PNPNL loop residue His-624 in HasR and of His-221 in its N-terminal plug domain required for heme capture to heme transport and signaling, respectively. Specifically, we show that substitution of the N-terminal plug His-221 disrupts both signaling and transport, leading to dysregulation of both the Has and Phu uptake systems. Our results are consistent with a model wherein heme release from HasAp to the N-terminal plug of HasR is required to initiate signaling, whereas His-624 is required for simultaneously closing off the heme transport channel from the extracellular medium and triggering heme transport. Our results provide critical insight into heme release, signaling, and transport in P. aeruginosa and suggest a functional link between the ECF σ factor and Phu heme uptake system.

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

2004 ◽  
Vol 186 (13) ◽  
pp. 4067-4074 ◽  
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.

scholarly journals Importance of the Ornibactin and Pyochelin Siderophore Transport Systems in Burkholderia cenocepacia Lung Infections

2004 ◽  
Vol 72 (5) ◽  
pp. 2850-2857 ◽  
Author(s):  
M. B. Visser ◽  
S. Majumdar ◽  
E. Hani ◽  
P. A. Sokol
Keyword(s):  
Salicylic Acid ◽  
Outer Membrane ◽  
Parent Strain ◽  
Membrane Receptor ◽  
Burkholderia Cenocepacia ◽  
Transport Systems ◽  
Uptake System ◽  
Outer Membrane Receptor ◽  
Gene Encoding ◽  
Lung Infections

ABSTRACT Previously, orbA, the gene encoding the outer membrane receptor for ferric-ornibactin, was identified in Burkholderia cenocepacia K56-2, a strain which produces ornibactin, salicylic acid, and negligible amounts of pyochelin. A K56-2 orbA mutant was less virulent than the parent strain in a rat agar bead infection model. In this study, an orbA mutant of B. cenocepacia Pc715j which produces pyochelin in addition to ornibactin and salicylic acid was constructed. The gene encoding the outer membrane receptor for ferric-pyochelin (fptA) was also identified. An fptA mutant was constructed in Pc715j and shown to be deficient in [59Fe]pyochelin uptake. A 75-kDa iron-regulated protein was identified in outer membrane preparations of Pc715j that was absent in outer membrane preparations of Pc715jfptA::tp. Pc715jfptA::tp and Pc715jorbA::tp produced smaller amounts of their corresponding siderophores. Both Pc715jorbA::tp and Pc715jfptA::tp were able to grow in iron starvation conditions in vitro. In the agar bead model, the Pc715jorbA::tp mutant was cleared from the lung, indicating that the pyochelin uptake system does not compensate for the absence of a functional ornibactin system. Pc715jfptA::tp persisted in rat lung infections in numbers similar to those of the parent strain, indicating that the ferric-ornibactin uptake system could compensate for the defect in ferric-pyochelin uptake in vivo. These studies suggest that the ornibactin uptake system is the most important siderophore-mediated iron transport system in B. cenocepacia lung infections.

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