Structure of the Ferrichrome Compounds<sup>1,2</sup>

Emery, Thomas; Neilands, J. B.

doi:10.1021/ja01468a020

Cited by 92 publications

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“…The ferrichromes comprise one large family of hydroxamate siderophores (Figure 1(a)) and were isolated from low-iron cultures of many fungi. 24 With few exceptions, ferrichromes possess cyclic hexapeptide backbones in which one tripeptide is linked to a second tripeptide of N δ -acyl-N δ -hydroxy-Lornithine. Linear derivatives of the latter tripeptide form backbones of various antibiotics, termed albomycines.…”

Section: Hydroxamate-type Siderophoresmentioning

confidence: 99%

Iron Transport: Siderophores

Matzanke

2005

Encyclopedia of Inorganic Chemistry

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Siderophores (from the Greek: iron carrier) are low molecular mass (500–1500 Da) iron chelators that are synthesized in bacteria and fungi under conditions of iron deficiency. Siderophores exhibit extraordinarily high complex formation constants for ferric iron with β‐values ranging from 10 20 to approximately 10 50 . Fe 2+ ‐siderophores are some 20 orders of magnitude less stable than their Fe 3+ counterparts. The d5 electronic configuration of Fe 3+ rules out any crystal field stabilization energy and makes ferric iron complexes relatively labile with respect to isomerization and ligand exchange. Siderophores display a selectivity for iron that is reflected in the corresponding complex stability constants that are higher with Fe 3+ than with Al 3+ , or with bivalent cations like Ca 2+ , Cu 2+ or Zn 2+ . Microorganisms excrete desferrisiderophores in order to scavenge iron from the environment. The competition for iron by siderophores, the mechanisms of siderophore uptake through microbial membranes, and the intracellular pathways of siderophore‐iron utilization strongly depend on thermodynamic, kinetic, and structural features of the ferric iron siderophore complexes. The structural features of siderophores are diverse. The ligating groups contain oxygen atoms of hydroxamate, catecholate, α‐hydroxy carboxylic and salicylic acids, or oxazoline and thiazoline nitrogen. Reduction potentials of ferric siderophore complexes vary between −700 and −150 mV. In particular at the low potential end below −450 mV, special biological strategies of reductive iron removal are required because these potentials are too negative for typical cellular reductases. The coordination and redox chemistry of siderophores is also reflected in the mechanisms of siderophore‐mediated iron uptake in microorganisms. A classic example is the intracellular removal of iron from enterobactin. The permeation of cell walls or bacterial membranes by siderophores is in most microbes a highly specific process requiring an array of up to eight proteins. The advent of modern molecular biology delivered a cornucopia of methods enabling high‐yield production of specific gene products relevant to siderophore synthesis and transport, analyses of structure‐function relationships (employing site directed mutagenesis), and detailed insights into the regulation of the corresponding processes. One siderophore, ferrioxamine B, serves as a detoxifier in iron overload diseases and in the treatment of β‐thalassemia. Siderophores and siderophore analogs also play a role in MRI and are employed as basic models for actinide chelators in order to remove these metals from the environment or from a contaminated body.

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Section: Hydroxamate-type Siderophoresmentioning

confidence: 99%

Iron Transport: Siderophores

Matzanke

2005

Encyclopedia of Inorganic Chemistry

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“…The third amino acid of this latter amino acid triplet is always glycine. Ferrichrome [20] is cyclo-triglycinetri-N 5 -hydroxy-N 5 -acetyl-L-orithine ( Figure 4). Ferricrocin [21] carries a serine in the second position of the amino acid triplet.…”

Section: Siderophores Containing Oligopeptidesmentioning

confidence: 99%

Peptide siderophores

1998

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Siderophores are low molecular weight iron chelators, produced by virtually all bacteria, fungi and some plants. They serve to deliver the essential element iron, barely soluble under aerobic conditions, into microbial cells. Siderophores are therefore important secondary metabolites which are very often based on amino acids and their derivatives. Biosynthesis, transport, regulation and chemical synthesis of natural siderophores and their analogues is of considerable interest for the protein and peptide chemist. This review gives an overview of the structural classes of peptidic siderophores, along with data on their biosynthesis. On a number of representative examples, strategies and schemes of their chemical synthesis are described.

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“…However, the mechanism of interaction between the siderophore and its recognition and transport sites in fungi is largely unknown (Winkelmann, 1993) , although there is evidence that the metal centre and its surrounding residues are likewise crucial for siderophore recognition and transport in fungi (Huschka et al, 1986;Winkelmann & Huschka, 1987 (Emery & Neilands, 1961). Ferrichrome-iron uptake in U .…”

Section: 52) a Large Number Of Siderophores Of Various Chemical Smentioning

confidence: 99%

Iron uptake in Ustilago maydis: studies with fluorescent ferrichrome analogues

et al. 1997

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Iron uptake by the phytopathogenic fungus Ustilago maydis was studied using synthetic biomimetic ferrichrome analogues and their fluorescently labelled derivatives as structural and dynamic probes, respectively. The use of structurally distinct analogues enabled determination of the structural requirements for recognition by the fungal iron-uptake system. The application of fluorescently labelled derivatives which convert from a non-fluorescent to a fluorescent state upon iron (III) release enabled monitoring of iron uptake in real time both fluorimetrically and microscopically. Different rates of 55Fe uptake were found for two structurally distinct synthetic analogues, B9 and B5, which differ in their amino acid building blocks. B9 mediated uptake of 55Fe at a higher rate than B5. The behaviour of the fluorescent derivatives B9-Ant (anthracene-labelled B9) and B5-Ant (anthracene-labelled B5) paralleled that of their non-labelled precursors. Exposure of fungal cells to B9-Ant led to a higher increase of fluorescence in the medium than exposure to B5-Ant, indicating a more effective iron uptake from B9-Ant. By using fluorescence microscopy it was possible to trace the label of B9-Ant. Fluorescence was localized in regularly shaped vesicles in the treated cells. The rate of fluorescence appearance within the cells lagged behind the rate of iron uptake, suggesting use of the siderophores for iron storage.

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Structure of the Ferrichrome Compounds^1,2

Cited by 92 publications

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Iron Transport: Siderophores

Iron Transport: Siderophores

Peptide siderophores

Iron uptake in Ustilago maydis: studies with fluorescent ferrichrome analogues

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Structure of the Ferrichrome Compounds1,2

Cited by 92 publications

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Iron Transport: Siderophores

Iron Transport: Siderophores

Peptide siderophores

Iron uptake in Ustilago maydis: studies with fluorescent ferrichrome analogues

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Structure of the Ferrichrome Compounds^1,2