Rubredoxin
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2008-04-28T11:49:15Z
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'''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 protein]]s; however, in contrast to iron-sulfur proteins, rubredoxins do not contain inorganic sulfide.
Like [[cytochrome]]s, [[ferredoxin]]s and [[Rieske protein]]s, 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 Fe<sub>1</sub>S<sub>0</sub> 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 state]]s. 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).
[[Image:Rubredoxin.png|frame|none|''Structural representation of a rubredoxin active site.'']]
==Rubredoxin in some biochemical reactions==
{{EC number|1.14.15.2}} camphor 1,2-monooxygenase [(+)-camphor,reduced-rubredoxin:oxygen oxidoreductase (1,2-lactonizing)]
: (+)-bornane-2,5-dione + reduced rubredoxin + O<sub>2</sub> = 5-oxo-1,2-campholide + oxidized rubredoxin + H<sub>2</sub>O
{{EC number|1.14.15.3}} alkane 1-monooxygenase (alkane,reduced-rubredoxin:oxygen 1-oxidoreductase)
: octane + reduced rubredoxin + O<sub>2</sub> = 1-octanol + oxidized rubredoxin + H<sub>2</sub>O
{{EC number|1.15.1.2}} superoxide reductase (rubredoxin:superoxide oxidoreductase)
: reduced rubredoxin + superoxide + 2 H<sup>+</sup> = rubredoxin + H<sub>2</sub>O<sub>2</sub>
{{EC number|1.18.1.1}} rubredoxin—NAD<sup>+</sup> reductase (rubredoxin:NAD<sup>+</sup> oxidoreductase)
: reduced rubredoxin + NAD<sup>+</sup> = oxidized rubredoxin + NADH + H<sup>+</sup>
{{EC number|1.18.1.4}} rubredoxin—NAD(P)<sup>+</sup> reductase (rubredoxin:NAD(P)<sup>+</sup> oxidoreductase)
: reduced rubredoxin + NAD(P)<sup>+</sup> = oxidized rubredoxin + NAD(P)H + H<sup>+</sup>
==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''
* {{InterPro|IPR001052}} - InterPro entry for rubredoxin
* [http://faculty.washington.edu/stenkamp/rubre.html A Little Iron-Sulfur Protein]
[[Category:Iron-sulfur proteins]]
[[Category:Metalloproteins]]
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