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

Many microbes and fungi acquire the essential ion Fe(3+) 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 ou...

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Autores principales: Josts, Inokentijs, Veith, Katharina, Tidow, Henning
Formato: Online Artículo Texto
Lenguaje:English
Publicado: eLife Sciences Publications, Ltd 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6699858/
https://www.ncbi.nlm.nih.gov/pubmed/31385808
http://dx.doi.org/10.7554/eLife.48528
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author Josts, Inokentijs
Veith, Katharina
Tidow, Henning
author_facet Josts, Inokentijs
Veith, Katharina
Tidow, Henning
author_sort Josts, Inokentijs
collection PubMed
description Many microbes and fungi acquire the essential ion Fe(3+) 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.
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spelling pubmed-66998582019-08-21 Ternary structure of the outer membrane transporter FoxA with resolved signalling domain provides insights into TonB-mediated siderophore uptake Josts, Inokentijs Veith, Katharina Tidow, Henning eLife Structural Biology and Molecular Biophysics Many microbes and fungi acquire the essential ion Fe(3+) 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. eLife Sciences Publications, Ltd 2019-08-06 /pmc/articles/PMC6699858/ /pubmed/31385808 http://dx.doi.org/10.7554/eLife.48528 Text en © 2019, Josts et al http://creativecommons.org/licenses/by/4.0/ http://creativecommons.org/licenses/by/4.0/This article is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use and redistribution provided that the original author and source are credited.
spellingShingle Structural Biology and Molecular Biophysics
Josts, Inokentijs
Veith, Katharina
Tidow, Henning
Ternary structure of the outer membrane transporter FoxA with resolved signalling domain provides insights into TonB-mediated siderophore uptake
title Ternary structure of the outer membrane transporter FoxA with resolved signalling domain provides insights into TonB-mediated siderophore uptake
title_full Ternary structure of the outer membrane transporter FoxA with resolved signalling domain provides insights into TonB-mediated siderophore uptake
title_fullStr Ternary structure of the outer membrane transporter FoxA with resolved signalling domain provides insights into TonB-mediated siderophore uptake
title_full_unstemmed Ternary structure of the outer membrane transporter FoxA with resolved signalling domain provides insights into TonB-mediated siderophore uptake
title_short Ternary structure of the outer membrane transporter FoxA with resolved signalling domain provides insights into TonB-mediated siderophore uptake
title_sort ternary structure of the outer membrane transporter foxa with resolved signalling domain provides insights into tonb-mediated siderophore uptake
topic Structural Biology and Molecular Biophysics
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6699858/
https://www.ncbi.nlm.nih.gov/pubmed/31385808
http://dx.doi.org/10.7554/eLife.48528
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