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The cellular machinery of Ferroplasma acidiphilum is iron-protein-dominated


Ferroplasma is a genus of the Archaea, one of the three branches of the tree of life, and belongs to the order Thermoplasmatales (Euryarchaeota), which contains the most acidophilic microbes yet known. Ferroplasma species live in acid mine drainage, acidic pools and environments containing sulphidic ores such as pyrite and characterized by pH values of 0–2 and high concentrations of ferrous iron and other heavy metals1,2,3. F. acidiphilum strain YT is a chemoautotroph that grows optimally at pH 1.7 and gains energy by oxidizing ferrous iron and carbon by the fixation of carbon dioxide1. Here we show that 86% of 189 investigated cellular proteins of F. acidiphilum are iron-metalloproteins. These include proteins with deduced structural, chaperone and catalytic roles, not described as iron-metalloproteins in any other organism so far investigated. The iron atoms in the proteins seem to organize and stabilize their three-dimensional structures, to act as ‘iron rivets’. Analysis of proteins of the phylogenetic neighbour Picrophilus torridus and of the habitat neighbour Acidithiobacillus ferrooxidans revealed far fewer and only typical metalloproteins. F. acidiphilum therefore has a currently unique iron-protein-dominated cellular machinery and biochemical phylogeny.

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Figure 1: ‘Luminal metalloproteome’ of F. acidiphilum YT.


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We thank G. Wächtershäuser, R. Thauer, M. Wilson, A. Böck and A. Ballesteros for discussions. This research was supported by the Spanish Ministerio de Educación y Ciencia (MEC) (Ramón y Cajal contract to M.F. and a FPU Fellowship to A.B.), European Community Project ‘BIOMELI’, the Microbial Genomic Network Programme (GenoMik Plus) of the German Ministry for Education and Research (BMBF), and the DFG Priority Program ‘Mars and Terrestrial Planets’. K.N.T. thanks the Fonds der Chemischen Industrie for generous support.

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Correspondence to Manuel Ferrer.

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This file contains Supplementary Methods, Supplementary Figures S1 and S2 with legends and Supplementary Tables S1-S5. (PDF 1623 kb)

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Ferrer, M., Golyshina, O., Beloqui, A. et al. The cellular machinery of Ferroplasma acidiphilum is iron-protein-dominated. Nature 445, 91–94 (2007).

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