Rubredoxin

Rubredoxin
File:PDB 1s24 EBI.jpg rubredoxin domain ii from pseudomonas oleovorans
Identifiers
Symbol	Rubredoxin
Pfam	PF00301
Pfam clan	CL0045
InterPro	IPR004039
PROSITE	PDOC00179
SCOP	7rxn
SUPERFAMILY	7rxn
Available protein structures: Pfam structures PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

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

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 [1Fe-0S] or an Fe₁S₀ system, in analogy to the nomenclature for iron-sulfur proteins. While the vast majority of rubredoxins are soluble, there exists a membrane-bound rubredoxin referred to as rubredoxin A in oxygenic photoautotrophs.

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.

This iron-sulphur protein is an electron carrier, and it is easy to distinguish its metallic centre changes: the oxidized state is reddish (due to a ligand metal charge transfer), while the reduced state is colourless (because the electron transition has an energy of the infrared level, which is imperceptible for the human eye).

File:Rubredoxin.png

Structural representation of a rubredoxin active site.

Rubredoxin in some biochemical reactions

EC 1.14.15.2 camphor 1,2-monooxygenase [(+)-camphor,reduced-rubredoxin:oxygen oxidoreductase (1,2-lactonizing)]

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

EC 1.14.15.3 alkane 1-monooxygenase (alkane,reduced-rubredoxin:oxygen 1-oxidoreductase)

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

EC 1.15.1.2 superoxide reductase (rubredoxin:superoxide oxidoreductase)

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

EC 1.18.1.1 rubredoxin—NAD⁺ reductase (rubredoxin:NAD⁺ oxidoreductase)

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

EC 1.18.1.4 rubredoxin—NAD(P)⁺ reductase (rubredoxin:NAD(P)⁺ oxidoreductase)

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

See also

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

References

• Stephen J. Lippard, Jeremy M. Berg, Principles of Bioinorganic Chemistry, University Science Books, 1994, ISBN 0-935702-72-5
• 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

• PDB: 1IRO​ - X-ray structure of rubredoxin from Clostridium pasteurianum
• PDB: 1VCX​ - neutron diffraction structure of rubredoxin from Pyrococcus furiosus
• IPR001052 - InterPro entry for rubredoxin
• A Little Iron-Sulfur Protein