The iron-binding properties of aminochelin, the mono(catecholamide) siderophore of Azotobacter vinelandii

Khodr, Hicham; Hider, Robert C.; Duhme‐Klair, Anne‐Kathrin

doi:10.1007/s00775-002-0375-x

Cited by 24 publications

(21 citation statements)

References 21 publications

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“…When grown with amorphous Fe oxide (condition 4), A. vinelandii grows as fast, and reaches the same OD, as with high Fe and EDTA (condition 2), but the siderophore pool consists almost exclusively of vibrioferrin and DHBA, with aminochelin and azotochelin at very low levels. Notably, both vibrioferrin (pK a values of 5.1, 3.6, and 2.7 [43]) and DHBA (pK a ϭ 2.9) are negatively charged at the experimental pH (pH 6.9), unlike aminochelin (pK a values of 7.1, 10.2, and 12.1 [49]), the other hydrophilic siderophore of A. vinelandii, which is positively charged. The negative charge of vibrioferrin and DHBA favors adsorption on positively charged Fe-oxyhydroxides (at pH Ͻ8), which may help in the dissolution of Fe and explain their elevated production compared to that of all other siderophores under condition 4.…”

Section: Discussionmentioning

confidence: 97%

The Siderophore Metabolome of Azotobacter vinelandii

Baars

Zhang

Morel

et al. 2016

Appl Environ Microbiol

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In this study, we performed a detailed characterization of the siderophore metabolome, or "chelome," of the agriculturally important and widely studied model organism Azotobacter vinelandii. Using a new high-resolution liquid chromatography-mass spectrometry (LC-MS) approach, we found over 35 metal-binding secondary metabolites, indicative of a vast chelome in A. vinelandii. These include vibrioferrin, a siderophore previously observed only in marine bacteria. Quantitative analyses of siderophore production during diazotrophic growth with different sources and availabilities of Fe showed that, under all tested conditions, vibrioferrin was present at the highest concentration of all siderophores and suggested new roles for vibrioferrin in the soil environment. Bioinformatic searches confirmed the capacity for vibrioferrin production in Azotobacter spp. and other bacteria spanning multiple phyla, habitats, and lifestyles. Moreover, our studies revealed a large number of previously unreported derivatives of all known A. vinelandii siderophores and rationalized their origins based on genomic analyses, with implications for siderophore diversity and evolution. Together, these insights provide clues as to why A. vinelandii harbors multiple siderophore biosynthesis gene clusters. Coupled with the growing evidence for alternative functions of siderophores, the vast chelome in A. vinelandii may be explained by multiple, disparate evolutionary pressures that act on siderophore production.

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Section: Discussionmentioning

confidence: 97%

The Siderophore Metabolome of Azotobacter vinelandii

Baars

Zhang

Morel

et al. 2016

Appl Environ Microbiol

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“…Furthermore, these complexes may be persistent even in the presence of iron despite their relatively low-affinity constants. In the presence of Mo(VI)O 2 2-, aminochelin (Khodr et al 2002), azotochelin (Khodr et al 2002), and protochelin (Duhme et al 1997) dissolve Fe(III) hydroxide more slowly than in Mo-free systems, with dissolution most inhibited for azotochelin (Khodr et al 2002). In culture, the complexes are stable in the presence of EDTA bound iron ).…”

Section: Iron Molybdenum and Vanadium In Nitrogen-fixing Bacteriamentioning

confidence: 93%

“…However, there are a number of specific examples that require that we distinguish between the two. In the class of catecholate metallophores, protochelin is a triscatecholate ligand that exhibits a log b = 44.6 for Fe(III), actually slightly lower than the log b 3 of catecholate (log b 3 = 44.9) and slightly higher than aminochelin (log b 3 = 41.3) (Harrington et al 2012a;Khodr et al 2002;Martell et al 2005). Enterobactin (log b = 49) has an additional increase in complex stability due to the preorganization of the donor groups, suggesting that the two effects should be distinguished from each other (Loomis and Raymond 1991).…”

Section: Structural Factors Controlling Metallophore Complexation Of mentioning

confidence: 94%

“…The presence of multiple siderophores, in conjunction with the relatively high intercellular quotas for Mo, has led to much interest in their possible roles as metallophores in the uptake of Mo, as well as the effect of Mo binding on Fe uptake. Catecholate ligands are known to associate with molybdate at circumneutral pH; however, the stability constants of the molybdate complexes are significantly lower than those of the corresponding Fe(III) complexes (Table 1) (Bellenger et al 2007;Cornish and Page 2000;Duhme et al 1998;Khodr et al 2002). Furthermore, molybdate activity affects the ratios of metallophores produced during A. vinelandii growth (Cornish andPage 1995, 2000).…”

Section: Iron Molybdenum and Vanadium In Nitrogen-fixing Bacteriamentioning

confidence: 96%

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Metallophores and Trace Metal Biogeochemistry

et al. 2014

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Trace metal limitation not only affects the biological function of organisms, but also the health of ecosystems and the global cycling of elements. The enzymatic machinery of microbes helps to drive critical biogeochemical cycles at the macroscale, and in many cases, the function of metalloenzyme-mediated processes may be limited by the scarcity of essential trace metals. In response to these nutrient limitations, some organisms employ a strategy of exuding metallophores, biogenic ligands that facilitate the uptake of metal ions. For example, bacterial, fungal, and graminaceous plant species are known to use Fe(III)-binding siderophores for nutrient acquisition, providing the best known and most thoroughly studied example of metallophores. However, recent breakthroughs have suggested or established the role of metallophores in the uptake of several other metallic nutrients. Furthermore, these metallophores may influence environmental trace metal fate and transport beyond nutrient acquisition. These discoveries have resulted in a deeper understanding of trace metal geochemistry and its relationship to the cycling of carbon and nitrogen in natural systems. In this review, we provide an overview of the current state of knowledge on the biogeochemistry of metallophores in trace metal acquisition, and explore established and potential metallophore systems.Electronic supplementary material The online version of this article (

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“…1), which is produced by the free-living diazotroph Azotobacter vinelandii (Cornish and Page 1995). Catecholate siderophores are one of the few ligands that bind molybdate at circumneutral pH, although these complexes have significantly lower stability constants than those of the ligand with Fe(III) (Duhme et al 1998;Bellenger et al 2007;Khodr et al 2002;Cornish and Page 2000). Protochelin has been implicated in the specific transport of Mo and V (in addition to Fe) in A. vinelandii (Bellenger et al 2008a, b), which uses these metals in nitrogenase enzymes (Bellenger et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Trace metal complexation by the triscatecholate siderophore protochelin: structure and stability

et al. 2011

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Although siderophores are generally viewed as biological iron uptake agents, recent evidence has shown that they may play significant roles in the biogeochemical cycling and biological uptake of other metals. One such siderophore that is produced by A. vinelandii is the triscatecholate protochelin. In this study, we probe the solution chemistry of protochelin and its complexes with environmentally relevant trace metals to better understand its effect on metal uptake and cycling. Protochelin exhibits low solubility below pH 7.5 and degrades gradually in solution. Electrochemical measurements of protochelin and metal-protochelin complexes reveal a ligand half-wave potential of 200 mV. The Fe(III)Proto(3-) complex exhibits a salicylate shift in coordination mode at circumneutral to acidic pH. Coordination of Mn(II) by protochelin above pH 8.0 promotes gradual air oxidation of the metal center to Mn(III), which accelerates at higher pH values. The Mn(III)Proto(3-) complex was found to have a stability constant of log β(110) = 41.6. Structural parameters derived from spectroscopic measurements and quantum mechanical calculations provide insights into the stability of the Fe(III)Proto(3-), Fe(III)H(3)Proto, and Mn(III)Proto(3-) complexes. Complexation of Co(II) by protochelin results in redox cycling of Co, accompanied by accelerated degradation of the ligand at all solution pH values. These results are discussed in terms of the role of catecholate siderophores in environmental trace metal cycling and intracellular metal release.

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The iron-binding properties of aminochelin, the mono(catecholamide) siderophore of Azotobacter vinelandii

Cited by 24 publications

References 21 publications

The Siderophore Metabolome of Azotobacter vinelandii

The Siderophore Metabolome of Azotobacter vinelandii

Metallophores and Trace Metal Biogeochemistry

Trace metal complexation by the triscatecholate siderophore protochelin: structure and stability

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