Rubredoxins are a class of low-molecular-weight iron-containing proteins found in sulfur-metabolizing bacteria and archaea. Sometimes rubredoxins are classified as iron-sulfur proteins; however, in contrast to iron-sulfur proteins, rubredoxins do not contain inorganic sulfide. Like cytochromes, ferredoxins and Rieske proteins, rubredoxins participate in electron transfer in biological systems.

Structure

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The 3-D structures of a number of rubredoxins have been solved. The fold belongs to the α+β class, with 2 α-helices and 2-3 β-strands. Rubredoxin active site contains an iron ion which is coordinated by the sulfurs of four conserved cysteine residues forming an almost regular tetrahedron. This is sometimes denoted as a ^* or an Fe₁S₀ system, in analogy to the nomenclature for iron-sulfur proteins.

Rubredoxins perform one-electron transfer processes. The central iron atom changes between the +2 and +3 oxidation states. In both oxidation states, the metal remains high spin, which helps to minimize structural changes. The reduction potential of a rubredoxin is typically in the range +50 mV to -50 mV.

Rubredoxin in some biochemical reactions

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camphor 1,2-monooxygenase oxidoreductase (1,2-lactonizing)

(+)-bornane-2,5-dione + reduced rubredoxin + O₂ = 5-oxo-1,2-campholide + oxidized rubredoxin + H₂O

alkane 1-monooxygenase (alkane,reduced-rubredoxin:oxygen 1-oxidoreductase)

octane + reduced rubredoxin + O₂ = 1-octanol + oxidized rubredoxin + H₂O

superoxide reductase (rubredoxin:superoxide oxidoreductase)

reduced rubredoxin + superoxide + 2 H⁺ = rubredoxin + H₂O₂

rubredoxin—NAD⁺ reductase (rubredoxin:NAD⁺ oxidoreductase)

reduced rubredoxin + NAD⁺ = oxidized rubredoxin + NADH + H⁺

rubredoxin—NAD(P)⁺ reductase (rubredoxin:NAD(P)⁺ oxidoreductase)

reduced rubredoxin + NAD(P)⁺ = oxidized rubredoxin + NAD(P)H + H⁺

See also

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• Bioinorganic chemistry
• Iron-sulfur proteins
• Ferredoxin
• Cytochrome
• Rieske protein

References

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• Stephen J. Lippard, Jeremy M. Berg, Principles of Bioinorganic Chemistry, University Science Books, 1994, ISBN 0-935-70272-5
• J.J.R. Fraústo da Silva and R.J.P. Williams, The biological chemistry of the elements: The inorganic chemistry of life, 2nd Edition, Oxford University Press, 2001, ISBN 0-19-850848-4

External links

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• - X-ray structure of rubredoxin from Clostridium pasteurianum
• - neutron diffraction structure of rubredoxin from Pyrococcus furiosus
• - InterPro entry for rubredoxin

Chemistry | Biochemistry | Inorganic chemistry