scholarly journals Ternary structure of the outer membrane transporter FoxA with resolved signalling domain provides insights into TonB-mediated siderophore uptake

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Inokentijs Josts ◽  
Katharina Veith ◽  
Henning Tidow
Keyword(s):  
Complex Structure ◽  
Binding Constants ◽  
Membrane Transporter ◽  
Gram Negative Bacteria ◽  
Detailed Mechanism ◽  
High Affinity ◽  
Ferrioxamine B ◽  
Outer Membrane Transporter ◽  
Inner Membrane Protein ◽  
Ternary Structure

Many microbes and fungi acquire the essential ion Fe3+ through the synthesis and secretion of high-affinity chelators termed siderophores. In Gram-negative bacteria, these ferric-siderophore complexes are actively taken up using highly specific TonB-dependent transporters (TBDTs) located in the outer bacterial membrane (OM). However, the detailed mechanism of how the inner-membrane protein TonB connects to the transporters in the OM as well as the interplay between siderophore- and TonB-binding to the transporter is still poorly understood. Here, we present three crystal structures of the TBDT FoxA from Pseudomonas aeruginosa (containing a signalling domain) in complex with the siderophore ferrioxamine B and TonB and combine them with a detailed analysis of binding constants. The structures show that both siderophore and TonB-binding is required to form a translocation-competent state of the FoxA transporter in a two-step TonB-binding mechanism. The complex structure also indicates how TonB-binding influences the orientation of the signalling domain.

scholarly journals Crystal structures of the outer membrane transporter FoxA provide novel insights into TonB-mediated siderophore uptake and signalling

2019 ◽  
Author(s):  
Inokentijs Josts ◽  
Katharina Veith ◽  
Henning Tidow
Keyword(s):  
Crystal Structures ◽  
Complex Structure ◽  
Binding Constants ◽  
Membrane Transporter ◽  
Gram Negative Bacteria ◽  
Detailed Mechanism ◽  
High Affinity ◽  
Ferrioxamine B ◽  
Outer Membrane Transporter ◽  
Inner Membrane Protein

AbstractMany microbes and fungi acquire the essential ion Fe3+ through the synthesis and secretion of high-affinity chelators termed siderophores. In Gram-negative bacteria, these ferric-siderophore complexes are actively taken up using highly specific TonB-dependent transporters (TBDTs) located in the outer bacterial membrane (OM). However, the detailed mechanism of how the inner-membrane protein TonB connects to the transporters in the OM as well as the interplay between siderophore- and TonB-binding to the transporter is still poorly understood. Here, we present three crystal structures of the TBDT FoxA from Pseudomonas aeruginosa (containing a signalling domain) in complex with the siderophore ferrioxamine B and TonB and combine them with a detailed analysis of binding constants. The structures show that both siderophore and TonB-binding is required to form a translocation-competent state of the FoxA transporter in a two-step TonB-binding mechanism. The complex structure also indicates how TonB-binding influences the orientation of the signalling domain.

scholarly journals Predicting the Complex Structure and Functional Motions of the Outer Membrane Transporter and Signal Transducer FecA

2008 ◽  
Vol 94 (7) ◽  
pp. 2482-2491 ◽  
Author(s):  
Taner Z. Sen ◽  
Margaret Kloster ◽  
Robert L. Jernigan ◽  
Andrzej Kolinski ◽  
Janusz M. Bujnicki ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Complex Structure ◽  
Membrane Transporter ◽  
Signal Transducer ◽  
Outer Membrane Transporter

scholarly journals High-Affinity Interaction between Gram-Negative Flagellin and a Cell Surface Polypeptide Results in Human Monocyte Activation

2000 ◽  
Vol 68 (10) ◽  
pp. 5525-5529 ◽  
Author(s):  
Patrick F. McDermott ◽  
Federica Ciacci-Woolwine ◽  
James A. Snipes ◽  
Steven B. Mizel
Keyword(s):  
Cell Surface ◽  
Mutational Analysis ◽  
Hypervariable Region ◽  
Gram Negative Bacteria ◽  
Human Monocytes ◽  
Necrosis Factor Alpha ◽  
Potent Inducer ◽  
Gram Negative ◽  
High Affinity ◽  
Tnf Α

ABSTRACT Flagella from diverse gram-negative bacteria induce tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β) synthesis by human monocytes (F. Ciacci-Woolwine, P. F. McDermott, and S. B. Mizel, Infect. Immun. 67:5176–5185, 1999). In this study, we establish that purified flagellin (FliC or FljB), the major filament protein from Salmonella enterica serovar Enteritidis,S. enterica serovar Typhimurium, and Pseudomonas aeruginosa, is an extremely potent inducer of TNF-α production by human monocytes and THP-1 myelomonocytic cells. Fifty percent of maximal TNF-α production (EC50) was obtained with 1.5 × 10−11 M flagellin (0.75 ng/ml). Mutagenesis studies revealed that the central hypervariable region of flagellin is essential for the TNF-α-inducing activity of the protein. Although less active than the wild-type protein, a Salmonellaflagellin mutant composed of only the central hypervariable region retained substantial TNF-α-inducing activity at nanomolar concentrations. In contrast, the conserved amino- and carboxy-terminal regions are inactive. Mutational analysis of the hypervariable region revealed that it contains two equally active TNF-α-inducing domains. The ability of THP-1 cells to respond to purified flagellins is dramatically reduced by mild trypsin treatment of the cells. Taken together, our results demonstrate that the cytokine-inducing activity of flagellins from gram-negative bacteria results from the interaction of these proteins with high-affinity cell surface polypeptide receptors on monocytes.

scholarly journals Structural insights into a novel family of integral membrane siderophore reductases

2021 ◽  
Vol 118 (34) ◽  
pp. e2101952118
Author(s):  
Inokentijs Josts ◽  
Katharina Veith ◽  
Vincent Normant ◽  
Isabelle J. Schalk ◽  
Henning Tidow
Keyword(s):  
Iron Uptake ◽  
Bacterial Species ◽  
Gram Negative Bacteria ◽  
Inner Membrane ◽  
Gram Negative ◽  
Inner Membrane Protein ◽  
Uptake Studies ◽  
Structural Insights

Gram-negative bacteria take up the essential ion Fe3+ as ferric-siderophore complexes through their outer membrane using TonB-dependent transporters. However, the subsequent route through the inner membrane differs across many bacterial species and siderophore chemistries and is not understood in detail. Here, we report the crystal structure of the inner membrane protein FoxB (from Pseudomonas aeruginosa) that is involved in Fe-siderophore uptake. The structure revealed a fold with two tightly bound heme molecules. In combination with in vitro reduction assays and in vivo iron uptake studies, these results establish FoxB as an inner membrane reductase involved in the release of iron from ferrioxamine during Fe-siderophore uptake.

scholarly journals Recombinant expression, purification, crystallization and preliminary X-ray diffraction analysis of the C-terminal DUF490963–1138domain of TamB fromEscherichia coli

2014 ◽  
Vol 70 (9) ◽  
pp. 1272-1275 ◽  
Author(s):  
Inokentijs Josts ◽  
Rhys Grinter ◽  
Sharon M. Kelly ◽  
Khedidja Mosbahi ◽  
Aleksander Roszak ◽  
...  
Keyword(s):  
Recombinant Expression ◽  
Diffusion Method ◽  
Gram Negative Bacteria ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Partner Protein ◽  
Experimental Phasing ◽  
Inner Membrane Protein ◽  
K 12

TamB is a recently described inner membrane protein that, together with its partner protein TamA, is required for the efficient secretion of a subset of autotransporter proteins in Gram-negative bacteria. In this study, the C-terminal DUF490963–1138domain of TamB was overexpressed inEscherichia coliK-12, purified and crystallized using the sitting-drop vapour-diffusion method. The crystals belonged to the primitive trigonal space groupP3121, with unit-cell parametersa=b= 57.34,c= 220.74 Å, and diffracted to 2.1 Å resolution. Preliminary secondary-structure and X-ray diffraction analyses are reported. Two molecules are predicted to be present in the asymmetric unit. Experimental phasing using selenomethionine-labelled protein will be undertaken in the future.

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