Structure of azoverdin, a pyoverdin-like siderophore of Azomonas macrocytogenes ATCC 12334

Linget, C.; Collinson, S. Karen; Azadi, Parastoo; Dell, Anne; Page, William; Abdallah, Mohamed Abou-Elwafa

doi:10.1016/s0040-4039(00)74169-4

Cited by 11 publications

(4 citation statements)

References 8 publications

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“…Under iron deficient conditions Azotobacter vinelandii (strain D) secretes high amounts of a fluorescent siderophore called azotobactin, a chromopeptidic siderophore belonging to the class of pyoverdins, the peptidic siderophores of the fluorescent pseudomonads . Pyoverdins are constituted of a fluorescent chromophore derived from 2,3-diamino-6,7-dihydroxyquinoline, bound via a carboxylic acid group to the N terminus of an oligopeptide of 6−12 amino acids of various chirality and composition with a linear, − partially cyclic, − or fully cyclic backbone.…”

Section: Introductionmentioning

confidence: 99%

Bacterial Iron Transport: Coordination Properties of Azotobactin, the Highly Fluorescent Siderophore ofAzotobacter vinelandii

et al. 2003

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Azotobacter vinelandii, a nitrogen-fixing soil bacterium, secretes in iron deficiency azotobactin delta, a highly fluorescent pyoverdin-like chromopeptidic hexadentate siderophore. The chromophore, derived from 2,3-diamino-6,7 dihydroxyquinoline, is bound to a peptide chain of 10 amino acids: (L)-Asp-(D)-Ser-(L)-Hse-Gly-(D)-beta-threo-HOAsp-(L)-Ser-(D)-Cit-(L)-Hse-(L)-Hse lactone-(D)-N(delta)-Acetyl, N(delta)-HOOrn. Azotobactin delta has three different iron(III) binding sites which are one hydroxamate group at the C-terminal end of the peptidic chain (N(delta)-Acetyl, N(delta)-HOOrn), one alpha-hydroxycarboxylic function in the middle of the chain (beta-threo-hydroxyaspartic acid), and one catechol group on the chromophore. The coordination properties of its iron(III) and iron(II) complexes were measured by spectrophotometry, potentiometry, and voltammetry after the determination of the acid-base functions of the uncomplexed free siderophore. Strongly negatively charged ferric species were observed at neutral p[H]'s corresponding to a predominant absolute configuration Lambda of the ferric complex in solution as deduced from CD measurements. The presence of an alpha-hydroxycarboxylic chelating group does not decrease the stability of the iron(III) complex when compared to the main trishydroxamate siderophores or to pyoverdins. The value of the redox potential of ferric azotobactin is highly consistent with a reductive step by physiological reductants for the iron release. Formation and dissociation kinetics of the azotobactin delta ferric complex point out that both ends of this long siderophore chain get coordinated to Fe(III) before the middle. The most striking result provided by fluorescence measurements is the lasting quenching of the fluorophore in the course of the protonation of the ferric azotobactin delta complex. Despite the release of the hydroxyacid and of the catechol, the fluorescence remains indeed quenched, when iron(III) is bound only to the hydroxamic acid, suggesting a folded conformation at this stage, around the metal ion, in contrast to the unfolded species observed for other siderophores such as ferrioxamine or pyoverdin PaA.

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Section: Introductionmentioning

confidence: 99%

Bacterial Iron Transport: Coordination Properties of Azotobactin, the Highly Fluorescent Siderophore ofAzotobacter vinelandii

et al. 2003

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“…These bidentate groups bind iron(III) with extremely high affinity giving very stable octahedral complexes. The primary structure of azoverdin was first reported to be a chromopeptide with a chromophore derived from 2,3-diamino-6,7-dihydroxyquinoline bound to a peptide chain containing two homoserines, one serine and two N δ -hydroxyornithines ( , ). In addition, a new amidine type of amino acid is present in the peptide chain: (1‘-amino,3‘-hydroxy)-2-propyl-4-carboxy-3,4,5,6-tetrahydro-pyrimidine, resulting from the condensation of one homoserine with 2,4-diaminobutyric acid (Dab).…”

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“…These bidentate groups bind iron(III) with extremely high affinity giving very stable octahedral complexes. The primary structure of azoverdin was first reported to be a chromopeptide with a chromophore derived from 2,3diamino-6,7-dihydroxyquinoline bound to a peptide chain containing two homoserines, one serine and two N δ -hydroxyornithines (15,28). Two primary sequences of azoverdin have been published that differed in the sequence of the peptide chain and in the site of covalent linkage on the chromophore (15,16).…”

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The Three-Dimensional Structure of the Gallium Complex of Azoverdin, a Siderophore of Azomonas macrocytogenes ATCC 12334, Determined by NMR Using Residual Dipolar Coupling Constants

Wasielewski¹,

Atkinson²,

Abdallah³

et al. 2002

Biochemistry

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In iron-deficient conditions, Azomonas macrocytogenes ATCC 12334 excretes a fluorescent siderophore called azoverdin, which is composed of a six-amino-acid peptide chain linked to a chromophore. Azoverdin chelates iron(III) very strongly, solubilizing it and transporting it back into the cells using an outer-membrane receptor. This compound is related to the pyoverdins, the peptidic siderophores of Pseudomonas, but differs in the site on the chromophore at which the peptide is covalently linked. This feature identifies azoverdin as a member of a new class of pyoverdins: the isopyoverdins. We report the three-dimensional structure of azoverdin-Ga(III) in solution. The use of orientational constraints obtained from the measurement of residual dipolar couplings using samples dissolved in a liquid crystalline medium allowed us to define the absolute configuration of the metal complex, which is Delta. The structure is characterized by a U-shape adopted by the peptide chain, with the N(delta)-acetyl-N(delta)-hydroxyornithine side chains adopting extended conformations in order to chelate the gallium ion. This conformation leaves a large open space permitting access to the gallium ion. The structural consequences of the particular isopyoverdin chemical structure are discussed in the context of the three-dimensional structures of other pyoverdins.

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“…The majority of soil microorganisms form siderophores containing hydroxamate ligands (2); levels of hydroxamate-type siderophores in soil have been reported to be as high as 10 ,uM (5), which should be sufficient to support the growth of bradyrhizobia (9). We have focused on three different siderophores: (i) the hydroxamate ferrichrome, which is probably the most commonly produced fungal siderophore; (ii) rhodotorulic acid, another hydroxamate-type siderophore which is synthesized by many yeast and smut fungi; and (iii) pseudobactin St3, which is one of many pyoverdin-type siderophores produced by fluorescent pseudomonads, as well as by various Azotobacter and Azomonas strains (e.g., 6,15). We also wanted to extend our observations on the utilization of exogenously supplied siderophores to B. japonicum USDA 110, given its use in commercial inocula and its role as the B. japonicum strain of choice for molecular genetic studies.…”

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Siderophore Utilization by Bradyrhizobium japonicum

Plessner

Klapatch

Guerinot

1993

Appl Environ Microbiol

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Structure of azoverdin, a pyoverdin-like siderophore of Azomonas macrocytogenes ATCC 12334

Cited by 11 publications

References 8 publications

Bacterial Iron Transport: Coordination Properties of Azotobactin, the Highly Fluorescent Siderophore ofAzotobacter vinelandii

Bacterial Iron Transport: Coordination Properties of Azotobactin, the Highly Fluorescent Siderophore ofAzotobacter vinelandii

The Three-Dimensional Structure of the Gallium Complex of Azoverdin, a Siderophore of Azomonas macrocytogenes ATCC 12334, Determined by NMR Using Residual Dipolar Coupling Constants

Siderophore Utilization by Bradyrhizobium japonicum

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