Synthesis and biological activity of pyochelin, a siderophore of Pseudomonas aeruginosa

Ankenbauer, Robert G.; Toyokuni, Tatsushi; Staley, Andrew L.; Rinehart, Kenneth L.; Cox, Charles D.

doi:10.1128/jb.170.11.5344-5351.1988

Cited by 86 publications

(74 citation statements)

References 51 publications

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“…Pyochelin has been assigned the structure 2-[2-(o-hydroxyphenyl) -2-thiazolin-4-yl] -3-methyl-4-thiazolidinecarboxylic acid and apparently chelates Fe(III) in a 2:1 pyochelin-Fe(III) stoichiometry (5,17). Two other pseudomonads, Pseudomonas cepacia and Pseudomonas fluorescens, also produce pyochelin (18,51).…”

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FptA, the Fe(III)-pyochelin receptor of Pseudomonas aeruginosa: a phenolate siderophore receptor homologous to hydroxamate siderophore receptors

1994

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The Pseudomonas aeruginosa siderophore pyochelin is structurally unique among siderophores and possesses neither hydroxamate- nor catecholate-chelating groups. The structural gene encoding the 75-kDa outer membrane Fe(III)-pyochelin receptor FptA has been isolated by plasmid rescue techniques and sequenced. The N-terminal amino acid sequence of the isolated FptA protein corresponded to that deduced from the nucleotide sequence of the fptA structural gene. The mature FptA protein has 682 amino acids and a molecular mass of 75,993 Da and has considerable overall homology with the hydroxamate siderophore receptors FpvA of P. aeruginosa, PupA and PupB of Pseudomonas putida, and FhuE of Escherichia coli. This observation indicates that homologies between siderophore receptors are an unreliable predictor of siderophore ligand class recognition by a given receptor. The fptA gene was strongly regulated by iron; fptA transcription was totally repressed by 30 microM FeCl3, as determined by Northern (RNA) blotting. The promoter of the fptA gene contained the sequence 5'-ATAATGATAAGCATTATC-3', which matches the consensus E. coli Fur-binding site at 17 of 18 positions. The -10 promoter region and transcriptional start site of the fptA gene reside within this Fur-binding site.

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FptA, the Fe(III)-pyochelin receptor of Pseudomonas aeruginosa: a phenolate siderophore receptor homologous to hydroxamate siderophore receptors

1994

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“…Pch is synthesized by P. aeruginosa from salicylate and two molecules of cysteine via a thiotemplate mechanism (11, 12) involving proteins encoded by the two biosynthetic operons pchDCBA and pchEFGHI (13,14). Pch biosynthesis is autoregulated by a positive-feedback loop (14) requiring the transcriptional regulator PchR together with Pch as an effector molecule (15,16).In the extracellular medium Pch chelates Fe 3ϩ with a 2:1 (Pvd:Fe 3ϩ ) stoichiometry (10,17,18), with one molecule of Pch tetradentately coordinated to Fe 3ϩ and the second molecule bound bidentately to complete the octahedral geometry (19). Pch has poor water solubility, and its Fe 3ϩ affinity was determined in ethanol as 2 ϫ 10 5 M (10).…”

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“…In the extracellular medium Pch chelates Fe 3ϩ with a 2:1 (Pvd:Fe 3ϩ ) stoichiometry (10,17,18), with one molecule of Pch tetradentately coordinated to Fe 3ϩ and the second molecule bound bidentately to complete the octahedral geometry (19). Pch has poor water solubility, and its Fe 3ϩ affinity was determined in ethanol as 2 ϫ 10 5 M (10).…”

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Stereospecificity of the Siderophore Pyochelin Outer Membrane Transporters in Fluorescent Pseudomonads

Hoegy

Lee

Noël

et al. 2009

Journal of Biological Chemistry

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Pyochelin (Pch) and enantio-pyochelin (EPch) are enantiomer siderophores that are produced by Pseudomonas aeruginosa and Pseudomonas fluorescens, respectively, under iron limitation. Pch promotes growth of P. aeruginosa when iron is scarce, and EPch carries out the same biological function in P. fluorescens. However, the two siderophores are unable to promote growth in the heterologous species, indicating that siderophore-mediated iron uptake is highly stereospecific. In the present work, using binding and iron uptake assays, we found that FptA, the Fe-Pch outer membrane transporter of P. aeruginosa, recognized (K d ‫؍‬ 2.5 ؎ 1.1 nM) and transported Fe-Pch but did not interact with Fe-EPch. Likewise, FetA, the Fe-EPch receptor of P. fluorescens, was specific for Fe-EPch (K d ‫؍‬ 3.7 ؎ 2.1 nM) but did not bind and transport Fe-Pch. Growth promotion experiments performed under iron-limiting conditions confirmed that FptA and FetA are highly specific for Pch and EPch, respectively. When fptA and fetA along with adjacent transport genes involved in siderophore uptake were swapped between the two bacterial species, P. aeruginosa became able to utilize Fe-EPch as an iron source, and P. fluorescens was able to grow with Fe-Pch. Docking experiments using the FptA structure and binding assays showed that the stereospecificity of Pch recognition by FptA was mostly due to the configuration of the siderophore chiral centers C4؆ and C2؆ and was only weakly dependent on the configuration of the C4 carbon atom. Together, these findings increase our understanding of the stereospecific interaction between Pch and its outer membrane receptor FptA.To access iron, aerobic bacteria produce siderophores which form complexes with Fe 3ϩ in the environment and deliver it via specific membrane transporters to the bacteria (1). The energy required for this process is provided by the proton motive force of the inner membrane by means of an inner membrane complex comprising TonB, ExbB, and ExbD (2, 3). Pyochelin (Pch), 2 which is the focus of this study, is produced as a secondary siderophore under iron limitation by almost all strains of Pseudomonas aeruginosa and some closely related bacteria (4 -7). In pseudomonads, secondary siderophores (pyochelin, thioquinolobactin, etc.) are usually produced in smaller amounts, demonstrate lower iron affinity, and are rather simple molecules compared with pyoverdin (the main siderophore). It is hypothesized that under certain environmental or physiological conditions, secondary siderophores provide sufficient iron to the cell or fulfill functions other than iron sequestration (8). Pch was isolated for the first time from P. aeruginosa ATCC 15692 by Liu and Shokrani (9), and its structure was established later by Cox et al. (10) as (4ЈR,2ЉR,4ЉR)-2Ј-(2-hydroxyphenyl)-3Љ-methyl-4Ј,5Ј,2Љ,3Љ,4Љ,5Љ-hexahydro-[4Ј,2Љ]bithiazolyl-4Љ-carboxylic acid with three chiral centers located at C4Ј, C2Љ, and C4Љ (see Fig. 1). Pch is synthesized by P. aeruginosa from salicylate and two molecules of cysteine via a thiot...

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“…1), which are produced and excreted by P. aeruginosa during iron limitation (12). Pyochelin synthesis starts from chorismate (13)(14)(15), a branch point intermediate in aromatic biosynthesis, and uses two molecules of L-cysteine ( Fig. 1).…”

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Isochorismate Synthase (PchA), the First and Rate-limiting Enzyme in Salicylate Biosynthesis of Pseudomonas aeruginosa

Gaille

Reimmann

Haas

2003

Journal of Biological Chemistry

103

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In Pseudomonas aeruginosa the extracellular metabolite and siderophore pyochelin is synthesized from two major precursors, chorismate and L-cysteine via salicylate as an intermediate. The regulatory role of isochorismate synthase, the first enzyme in the pyochelin biosynthetic pathway, was studied. This enzyme is encoded by pchA, the last gene in the pchDCBA operon. The PchA protein was purified to apparent electrophoretic homogeneity from a PchA-overexpressing P. aeruginosa strain. The native enzyme was a 52-kDa monomer in solution, and its activity strictly depended on Mg 2؉ . At pH 7.0, the optimum, a K m ‫؍‬ 4.5 M and a k cat ‫؍‬ 43.1 min ؊1 were determined for chorismate. No feedback inhibitors or other allosteric effectors were found. The intracellular PchA concentration critically determined the rate of salicylate formation both in vitro and in vivo. In cultures grown in iron-limiting media to high cell densities, overexpression of the pchA gene resulted in overproduction of salicylate as well as in enhanced pyochelin formation. From this work and earlier studies, it is proposed that one important factor influencing the flux through the pyochelin biosynthetic pathway is the PchA concentration, which is determined at a transcriptional level, with pyochelin acting as a positive signal and iron as a negative signal.

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Synthesis and biological activity of pyochelin, a siderophore of Pseudomonas aeruginosa

Cited by 86 publications

References 51 publications

FptA, the Fe(III)-pyochelin receptor of Pseudomonas aeruginosa: a phenolate siderophore receptor homologous to hydroxamate siderophore receptors

FptA, the Fe(III)-pyochelin receptor of Pseudomonas aeruginosa: a phenolate siderophore receptor homologous to hydroxamate siderophore receptors

Stereospecificity of the Siderophore Pyochelin Outer Membrane Transporters in Fluorescent Pseudomonads

Isochorismate Synthase (PchA), the First and Rate-limiting Enzyme in Salicylate Biosynthesis of Pseudomonas aeruginosa

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