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Siderophore activity of myo-inositol hexakisphosphate in Pseudomonas aeruginosa
A W Smith1, D R Poyner, H K Hughes
1Department of Pharmaceutical and Biological Sciences, Aston University, United Kingdom.
Abstract:
myo-Inositol hexakisphosphate (InsP6), which is found in soil and most, if not all, plant and animal cells, has been estimated to have an affinity for Fe3+ in the range of 10(25) to 10(30) M-1. In this report, we demonstrate that the Fe-InsP6 complex has siderophore activity and is able to reverse the iron-restricted growth inhibition of Pseudomonas aeruginosa by ethylene diamine di(o-hydroxyphenyl)acetic acid. With 55Fe-InsP6 in transport studies, iron uptake is strongly iron regulated, being repressed after growth in iron-replete conditions and inhibited by treatment with potassium cyanide and carbonyl cyanide m-chlorophenylhydrazone. The kinetics of iron transport revealed a Km of 100 nM. Self-displacement of binding of [3H]InsP6 to isolated membranes by InsP6 revealed a single class of binding sites (Kd = 143 +/- 6 nM; Hill coefficient, 1.1 +/- 0.1). The binding of [3H]InsP6 to membranes was not dependent on whether cells had been grown under conditions of high or low iron concentrations. We believe that this is the first report of inositol polyphosphate activity in prokaryotic cells.
Insights
myo-Inositol hexakisphosphate (InsP6) exhibits siderophore activity, effectively reversing iron-restricted growth in Pseudomonas aeruginosa. This study reveals InsP6
Area of Science:
- Microbiology
- Biochemistry
Background:
- myo-Inositol hexakisphosphate (InsP6) is abundant in soil and cells.
- InsP6 has a high affinity for Fe3+ (10^25–10^30 M-1).
Purpose of the Study:
- To investigate the siderophore activity of the Fe-InsP6 complex.
- To explore the role of InsP6 in iron uptake in prokaryotic cells.
Main Methods:
- Demonstrated Fe-InsP6 complex siderophore activity.
- Utilized 55Fe-InsP6 for iron transport studies.
- Analyzed InsP6 binding to isolated bacterial membranes.
Main Results:
- Fe-InsP6 reversed iron-restricted growth in Pseudomonas aeruginosa.
- Iron uptake via Fe-InsP6 was iron-regulated and inhibited by metabolic inhibitors.
- Identified a single class of InsP6 binding sites on bacterial membranes (Kd = 143 ± 6 nM).
Conclusions:
- The Fe-InsP6 complex possesses significant siderophore activity.
- This is the first report of inositol polyphosphate activity in prokaryotic cells.
- InsP6 plays a role in iron transport mechanisms in bacteria.