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Essential Metal Uptake in Gram-negative Bacteria: X-ray Fluorescence, Radioisotopes, and Cell Fractionation
Published on: February 1, 2018
A periplasmic iron-binding protein contributes toward inward copper supply
Kevin J Waldron1, Stephen Tottey, Sachiko Yanagisawa
1Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Newcastle NE4 2HH, United Kingdom.
The Journal of Biological Chemistry
|December 7, 2006
Summary
FutA2, a periplasmic protein, is crucial for copper import in Synechocystis. Mutants lacking FutA2 show impaired copper use, suggesting its role in metal partitioning to prevent iron interference.
Area of Science:
- Microbiology
- Biochemistry
- Cell Biology
Background:
- Periplasmic substrate binding proteins typically transport iron, zinc, manganese, nickel, and molybdenum, but their role in copper transport is less understood.
- Synechocystis PCC 6803 utilizes copper for essential functions like thylakoid-localized plastocyanin and cytochrome oxidase.
Purpose of the Study:
- To investigate the function of the periplasmic substrate binding protein FutA2 in copper metabolism in Synechocystis PCC 6803.
- To determine if FutA2 plays a role in copper transport or influences the uptake of other essential metals.
Main Methods:
- Analysis of `DeltafutA2` mutants under varying copper conditions.
- Two-dimensional native liquid chromatography for protein complex separation.
- Metal analysis and peptide mass-fingerprinting to identify bound metals and proteins.
- In vitro binding assays with recombinant FutA2.
Main Results:
- `DeltafutA2` mutants exhibited reduced cytochrome oxidase activity and produced cytochrome c6 under copper-limiting conditions.
- Copper-plastocyanin accumulation was impaired in `DeltafutA2` mutants, while iron-ferredoxin remained unaffected.
- Recombinant FutA2 preferentially bound iron over copper in vitro, with an affinity similar to FutA1.
- FutA2 was associated with iron, not copper, in periplasmic extracts, and this complex was absent in `DeltafutA2` mutants.
Conclusions:
- FutA2 plays a significant role in copper metabolism by potentially sequestering iron (Fe(III)) in the periplasm.
- This sequestration by FutA2 may prevent aberrant iron binding to essential sites for other metals, including copper.
- FutA2 contributes to maintaining metal homeostasis and partitioning within the periplasm.
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