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

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2013
Author Lin Po-Chi, Youard Zeb A., Reimmann Cornelia,
Project Enantio-pyochelin: Biosynthesis, regulation, and natural occurrence
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Original article (peer-reviewed)

Journal Biometals
Volume (Issue) 26(6)
Page(s) 1067 - 1073
Title of proceedings Biometals
DOI 10.1007/s10534-013-9676-5

Open Access


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.