Rieske proteins are

iron–sulfur protein Iron–sulfur proteins (or iron–sulphur proteins in British spelling) are proteins characterized by the presence of iron–sulfur clusters containing sulfide-linked di-, tri-, and tetrairon centers in variable oxidation states. Iron–sulfur clu ...

(ISP) components of cytochrome ''bc''₁ complexes and cytochrome b₆f complexes and are responsible for electron transfer in some biological systems. John S. Rieske and co-workers first discovered the protein and in 1964 isolated an acetylated form of the bovine mitochondrial protein. In 1979 Trumpower's lab isolated the "oxidation factor" from bovine

mitochondria A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...

and showed it was a reconstitutively-active form of the Rieske iron-sulfur protein
It is a unique Fe-2Scluster in that one of the two Fe atoms is coordinated by two

histidine Histidine (symbol His or H) is an essential amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated –NH3+ form under biological conditions), a carboxylic acid group (which is in the de ...

residues rather than two

cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. When present as a deprotonated catalytic residue, sometime ...

residues. They have since been found in plants, animals, and

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

with widely ranging electron

reduction potential Redox potential (also known as oxidation / reduction potential, ''ORP'', ''pe'', ''E_'', or E_) is a measure of the tendency of a chemical species to acquire electrons from or lose electrons to an electrode and thereby be reduced or oxidised respe ...

s from -150 to +400 mV.

Biological function

Ubiquinol-cytochrome-c reductase (also known as bc1 complex or complex III) is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

complex of bacterial and mitochondrial

oxidative phosphorylation Oxidative phosphorylation (UK , US ) or electron transport-linked phosphorylation or terminal oxidation is the metabolic pathway in which cells use enzymes to oxidize nutrients, thereby releasing chemical energy in order to produce adenosine tri ...

systems. It catalyses the

oxidation-reduction reaction Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...

of the mobile components

ubiquinol A ubiquinol is an electron-rich (reduced) form of coenzyme Q (ubiquinone). The term most often refers to ubiquinol-10, with a 10-unit tail most commonly found in humans. The natural ubiquinol form of coenzyme Q is 2,3-dimethoxy-5-methyl-6-poly ...

and

cytochrome c The cytochrome complex, or cyt ''c'', is a small hemeprotein found loosely associated with the inner membrane of the mitochondrion. It belongs to the cytochrome c family of proteins and plays a major role in cell apoptosis. Cytochrome c is hig ...

, contributing to an

electrochemical potential In electrochemistry, the electrochemical potential (ECP), ', is a thermodynamic measure of chemical potential that does not omit the energy contribution of electrostatics. Electrochemical potential is expressed in the unit of J/ mol. Introductio ...

difference across the mitochondrial inner or bacterial membrane, which is linked to

ATP synthesis ATP synthase is a protein that catalyzes the formation of the energy storage molecule adenosine triphosphate (ATP) using adenosine diphosphate (ADP) and inorganic phosphate (Pi). It is classified under ligases as it changes ADP by the formation ...

. The complex consists of three subunits in most bacteria, and nine in mitochondria: both bacterial and mitochondrial complexes contain

cytochrome b Cytochrome b within both molecular and cell biology, is a protein found in the mitochondria of eukaryotic cells. It functions as part of the electron transport chain and is the main subunit of transmembrane cytochrome bc1 and b6f complexes. F ...

and

cytochrome c1 Cytochrome C1 (also known as Complex III subunit 4) is a protein encoded by the ''CYC1'' gene. Cytochrome is a heme-containing subunit of the cytochrome b-c1 complex, which accepts electrons from Rieske protein and transfers electrons to cytochr ...

subunits, and an iron–sulfur 'Rieske' subunit, which contains a high potential 2Fe-2S cluster. The mitochondrial form also includes six other subunits that do not possess redox centres.

Plastoquinone Plastoquinone (PQ) is an isoprenoid quinone molecule involved in the electron transport chain in the light-dependent reactions of photosynthesis. The most common form of plastoquinone, known as PQ-A or PQ-9, is a 2,3-dimethyl-1,4-benzoquinone m ...

plastocyanin Plastocyanin is a copper-containing protein that mediates electron-transfer. It is found in a variety of plants, where it participates in photosynthesis. The protein is a prototype of the blue copper proteins, a family of intensely blue-colored m ...

reductase (b6f complex), present in

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

and the

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...

s of plants, catalyses the oxidoreduction of

plastoquinol Plastoquinone (PQ) is an isoprenoid quinone molecule involved in the electron transport chain in the light-dependent reactions of photosynthesis. The most common form of plastoquinone, known as PQ-A or PQ-9, is a 2,3-dimethyl-1,4-benzoquinone mol ...

and

cytochrome f Cytochrome ''f'' is the largest subunit of cytochrome ''b''6''f'' complex (plastoquinol—plastocyanin reductase; ). In its structure and functions, the cytochrome b6f complex bears extensive analogy to the cytochrome bc1 complex of mitochondr ...

. This complex, which is functionally similar to ubiquinol-cytochrome c reductase, comprises cytochrome b6, cytochrome f and Rieske subunits. The Rieske subunit acts by binding either a

anion, transferring an electron to the 2Fe-2S cluster, then releasing the electron to the

heme iron. The reduction of the Rieske center increases the affinity of the subunit by several orders of magnitude, stabilizing the

semiquinone Semiquinone (or ubisemiquinone) is a free radical resulting from the removal of one hydrogen atom with its electron during the process of dehydrogenation of a hydroquinone, such as hydroquinone itself or catechol, to a quinone or alternatively the ...

radical Radical may refer to: Politics and ideology Politics *Radical politics, the political intent of fundamental societal change *Radicalism (historical), the Radical Movement that began in late 18th century Britain and spread to continental Europe and ...

at the Q(P) site. The Rieske domain has a Fe-2Scenter. Two conserved

s coordinate one Fe ion while the other Fe ion is coordinated by two conserved histidines. The 2Fe-2S cluster is bound in the highly conserved C-terminal region of the Rieske subunit.

Rieske protein family

The homologues of the Rieske proteins include ISP components of cytochrome ''b''₆''f'' complex, aromatic-ring-hydroxylating dioxygenases (phthalate dioxygenase,

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...

naphthalene Naphthalene is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromati ...

and

toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon. It is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH3) at ...

1,2-dioxygenases) and arsenite oxidase ( ECbr>1.20.98.1
. Comparison of amino acid sequences has revealed the following consensus sequence: : Cys-Xaa-His-(Xaa)_15–17-Cys-Xaa-Xaa-His

3D structure

The crystal structures of a number of Rieske proteins are known. The overall fold, comprising two subdomains, is dominated by antiparallel β-structure and contains variable numbers of

α-helices The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located four residues ear ...

. The smaller "cluster-binding" subdomains in mitochondrial and chloroplast proteins are virtually identical, whereas the large subdomains are substantially different in spite of a common folding topology. The e₂S₂cluster-binding subdomains have the topology of an incomplete antiparallel β-barrel. One iron atom of the Rieske e₂S₂cluster in the domain is coordinated by two

residues and the other is coordinated by two

residues through the N^δ atoms. The ligands coordinating the cluster originate from two loops; each loop contributes one Cys and one His.

Subfamilies

* Rieske iron–sulfur protein, C-terminal * Arsenite oxidase, small subunit

Human proteins containing this domain

AIFM3 Apoptosis-inducing factor, mitochondria-associated 3 is a protein that in humans is encoded by the AIFM3 gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." m ...

; RFESD;

UQCRFS1 Ubiquinol-cytochrome c reductase, Rieske iron-sulfur polypeptide 1, also known as UQCRFS1, Rieske iron-sulfur (Fe-S) protein, Cytochrome b-c1 complex subunit 5, or Complex III subunit 5 is a protein which in humans is encoded by the ''UQCRFS1'' ge ...

;

References

External links

* - X-ray structure of Rieske protein (water-soluble fragment) of the bovine mitochondrial cytochrome ''bc''₁ complex * - X-ray structure of Rieske protein (water-soluble fragment) of the spinach chloroplast cytochrome ''b''₆'' f''complex * - X-ray structure of Rieske-type ferredoxin associated with biphenyl dioxygenase from '' Burkholderia cepacia'' * - X-ray structure of Rieske subunit of arsenite oxidase from ''Alcaligenes faecalis'' * - X-ray structure of the ''Sphingomonas yanoikuyae B1'' Rieske ferredoxin * - X-ray structure of the

Pseudomonas ''Pseudomonas'' is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 described species. The members of the genus demonstrate a great deal of metabolic diversity and consequently are able ...

Naphthalene 1,2-dioxygenase Rieske ferredoxin * {{InterPro, IPR005806 - InterPro entry for Rieske Fe-2Sregion Iron–sulfur proteins Protein domains Peripheral membrane proteins