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In vitro-binding of the natural siderophore enantiomers pyochelin and enantiopyochelin to their AraC-type regulators PchR in Pseudomonas

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Abstract

The enantiomeric siderophores pyochelin and enantiopyochelin of Pseudomonas aeruginosa and Pseudomonas protegens promote growth under iron limitation and activate transcription of their biosynthesis and uptake genes via the AraC-type regulator PchR. Here we investigated siderophore binding to PchR in vitro using fluorescence spectroscopy. A fusion of the N-terminal domain of P. aeruginosa PchR with maltose binding protein (MBP-PchR′PAO) bound iron-loaded (ferri-) pyochelin with an affinity (Kd) of 41 ± 5 μM. By contrast, no binding occurred with ferri-enantiopyochelin. Stereospecificity of a similar fusion protein of the P. protegens PchR (MBP-PchR′CHA0) was less pronounced. The Kd’s of MBP-PchR′CHA0 for ferri-enantiopyochelin and ferri-pyochelin were 24 ± 5 and 40 ± 7 μM, respectively. None of the proteins interacted with the iron-free siderophore enantiomers, suggesting that transcriptional activation by PchR occurs only when the respective siderophore actively procures iron to the cell.

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Acknowledgments

This work as supported by the Swiss National Foundation for scientific research (projects 31003A-132998 and 3100A0-113955).

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Authors and Affiliations

  1. Département de Microbiologie Fondamentale, Université de Lausanne, Bâtiment Biophore, Quartier UNIL-Sorge, 1015, Lausanne, Switzerland

    Po-Chi Lin, Zeb A. Youard & Cornelia Reimmann

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  1. Po-Chi Lin
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  2. Zeb A. Youard
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  3. Cornelia Reimmann
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Correspondence to Cornelia Reimmann.

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Lin, PC., Youard, Z.A. & Reimmann, C. In vitro-binding of the natural siderophore enantiomers pyochelin and enantiopyochelin to their AraC-type regulators PchR in Pseudomonas . Biometals 26, 1067–1073 (2013). https://doi.org/10.1007/s10534-013-9676-5

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