Molecular structure of FoxE, the putative iron oxidase of Rhodobacter ferrooxidans SW2

The ancient metabolism of photoferrotrophy is likely to have played a key role in the biogeochemical cycle of iron on Early Earth leading to the deposition of Banded Iron Formations prior to the emergence of oxygenic photosynthesis. Extant organisms still performing this metabolism provide a conveni...

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Published in:Biochimica et biophysica acta. Bioenergetics 2017-10, Vol.1858 (10), p.847-853
Main Authors: Pereira, Luis, Saraiva, Ivo H., Oliveira, A. Sofia F., Soares, Cláudio M., Louro, Ricardo O., Frazão, Carlos
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Crystallography
Cytochrome
Disulfides - chemistry
Electron transfer
Electron Transport - physiology
Electrons
Ferrous Compounds - chemistry
Heme - chemistry
Iron - chemistry
Molecular Structure
Oxidation-Reduction
Oxidoreductases - chemistry
Oxygen - chemistry
Photoferrotrophy
Photosynthesis - physiology
Rhodobacter - chemistry
Surface electrostatics
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Summary:The ancient metabolism of photoferrotrophy is likely to have played a key role in the biogeochemical cycle of iron on Early Earth leading to the deposition of Banded Iron Formations prior to the emergence of oxygenic photosynthesis. Extant organisms still performing this metabolism provide a convenient window to peer into its molecular mechanisms. Here we report the molecular structure of FoxE, the putative terminal iron oxidase of Rhodobacter ferrooxidans SW2. This protein is organized as a trimer with two hemes and a disulfide bridge per monomer. The distance between hemes, their solvent exposure and the surface electrostatics ensure a controlled electron transfer rate. They also guarantee segregation between electron capture from ferrous iron and electron release to downstream acceptors, which do not favor the precipitation of ferric iron. Combined with the functional characterization of this protein, the structure reveals how iron oxidation can be performed in the periplasmic space of this Gram-negative bacterium at circumneutral pH, while minimizing the risk of mineral precipitation and cell encrustation. •Crystal structure of phototrophic Rhodobacter ferrooxidans SW2 iron oxidase•Provides a view of the molecular mechanism of photoferrotrophy•A three-fold NCS oxidase, whose monomers harbor pairs of homologous cytochromes-c•The 3D structure suggests an intricate duplication of an ancestral gene•The structure reveals how iron terminal oxidation may safely occur in SW2 periplasm
ISSN:0005-2728
1879-2650
DOI:10.1016/j.bbabio.2017.07.002