InterPro domain: IPR014349

The Rieske subunit can be found in the Ubiquinol-cytochrome c reductase (bc1 complex or complex III) or the cytochrome b6f complex. The Rieske subunit acts by binding either a ubiquinol or plastoquinol anion, transferring an electron to the 2Fe-2S cluster, then releasing the electron to the cytochrome c or cytochrome f haem iron [ 1 , 2 ]. The 2Fe-2S cluster is bound in the highly conserved C-terminal region of the Rieske subunit.

Ubiquinol-cytochrome c reductase (bc1 complex or complex III) is an enzyme complex of bacterial and mitochondrial oxidative phosphorylation systems. It catalyses the oxidoreduction of the mobile redox components ubiquinol and cytochrome c, generating an electrochemical potential which is linked to ATP synthesis [ 3 , 3 ].The complex consists of three subunits in most bacteria, and nine in mitochondria: both bacterial and mitochondrial complexes contain cytochrome b and cytochrome c1 subunits, and an iron-sulphur `Rieske' subunit, which contains a high potential 2Fe-2S cluster [ 4 ]. The mitochondrial form also includes six other subunits that do not possess redox centres.

The plant cytochrome b6f is located in the thylakoid membrane and functions in both linear and cyclic electron transport, providing ATP and NADPH for photosynthetic carbon fixation. The cytochrome b6f complex has eight different subunits, six being encoded in the chloroplast genome (PetA [cyt f], PetB [cyt b6], PetD, PetG, PetL, and PetN) and two in the nucleus (PetC [Rieske FeS] and PetM. The complex functions as a dimer [ 5 ]. In cyanobacteria, the cytochrome b6f complex contains four large subunits, including cytochrome f, cytochrome b6, the Rieske iron-sulfur protein (ISP), and subunit IV; as well as four small hydrophobic subunits, PetG, PetL, PetM, and PetN [ 6 ].

Proteins in this entry also include arsenite oxidase subunit AioB from Alcaligenes faecalis. It is involved in the detoxification of arsenic [ 7 ].

1. The primary structure of the iron-sulfur subunit of ubiquinol-cytochrome c reductase from Neurospora, determined by cDNA and gene sequencing. Eur. J. Biochem. 149, 95-9
2. Import and processing of the precursor of the Rieske FeS protein of tobacco chloroplasts. Plant Mol. Biol. 20, 289-99
3. Nucleotide sequence and transcription of the fbc operon from Rhodopseudomonas sphaeroides. Evaluation of the deduced amino acid sequences of the FeS protein, cytochrome b and cytochrome c1. Eur. J. Biochem. 154, 569-79
4. The genes of the Paracoccus denitrificans bc1 complex. Nucleotide sequence and homologies between bacterial and mitochondrial subunits. J. Biol. Chem. 262, 13805-11
5. Overexpression of the RieskeFeS Protein Increases Electron Transport Rates and Biomass Yield. Plant Physiol. 175, 134-145
6. Structure of the cytochrome b6f complex of oxygenic photosynthesis: tuning the cavity. Science 302, 1009-14
7. Crystal structure of the 100 kDa arsenite oxidase from Alcaligenes faecalis in two crystal forms at 1.64 A and 2.03 A. Structure 9, 125-32