The coenzyme Q : cytochrome c – oxidoreductase, sometimes called the cytochrome bc1 complex, and at other times complex III, is the third complex in the electron transport chain, playing a critical role in biochemical generation of ATP. Complex III is a multisubunit transmembrane protein encoded by both the mitochondrial and the nuclear genomes. Complex III is present in the mitochondria of all animals and all aerobic eukaryotes and the inner membranes of most eubacteria. Mutations in Complex III cause exercise intolerance as well as multisystem disorders. The bc1 complex contains 11 subunits, 3 respiratory subunits, 2 core proteins and 6 low-molecular weight proteins.
Rieske proteins are iron–sulfur protein (ISP) components of cytochrome bc1 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 and showed it was a reconstitutively-active form of the Rieske iron-sulfur protein
It is a unique [2Fe-2S] cluster in that one of the two Fe atoms is coordinated by two histidine residues rather than two cysteine residues. They have since been found in plants, animals, and bacteria with widely ranging electron reduction potentials from -150 to +400 mV.
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.
Cytochrome c oxidase II is a protein in eukaryotes that is encoded by the MT-CO2 gene. Cytochrome c oxidase subunit II, abbreviated COXII, COX2, COII, or MT-CO2, is the second subunit of cytochrome c oxidase. It is also one of the three mitochondrial DNA (mtDNA) encoded subunits of respiratory complex IV.
Cytochrome c oxidase subunit III (COX3) is an enzyme that in humans is encoded by the MT-CO3 gene. It is one of main transmembrane subunits of cytochrome c oxidase. It is also one of the three mitochondrial DNA (mtDNA) encoded subunits of respiratory complex IV. Variants of it have been associated with isolated myopathy, severe encephalomyopathy, Leber hereditary optic neuropathy, mitochondrial complex IV deficiency, and recurrent myoglobinuria.
Cytochrome b is a protein that in humans is encoded by the MT-CYB gene. Its gene product is a subunit of the respiratory chain protein ubiquinol–cytochrome c reductase, which consists of the products of one mitochondrially encoded gene, MT-CYB, and ten nuclear genes—UQCRC1, UQCRC2, CYC1, UQCRFS1, UQCRB, "11kDa protein", UQCRH, Rieske protein presequence, "cyt c1 associated protein", and Rieske-associated protein.
Cytochrome c1, heme protein, mitochondrial (CYC1), also known as UQCR4, MC3DN6, Complex III subunit 4, Cytochrome b-c1 complex subunit 4, or Ubiquinol-cytochrome-c reductase complex cytochrome c1 subunit is a protein that in humans is encoded by the CYC1 gene. CYC1 is a respiratory subunit of Ubiquinol Cytochrome c Reductase, which is located in the inner mitochondrial membrane and is part of the electron transport chain. Mutations in this gene may cause mitochondrial complex III deficiency, nuclear, type 6.
Cytochrome b-c1 complex subunit 1, mitochondrial is a protein that in humans is encoded by the UQCRC1 gene.
Mitochondrial chaperone BCS1 (BCS1L), also known as BCS1 homolog, ubiquinol-cytochrome c reductase complex chaperone (h-BCS1), is a protein that in humans is encoded by the BCS1L gene. BCS1L is a chaperone protein involved in the assembly of Ubiquinol Cytochrome c Reductase, which is located in the inner mitochondrial membrane and is part of the electron transport chain. Mutations in this gene are associated with mitochondrial complex III deficiency, GRACILE syndrome, and Bjoernstad syndrome.
Ubiquinol-cytochrome c reductase complex , also known as UCRC or UQCR10, is a human gene.
Ubiquinol-cytochrome c reductase binding protein, also known as UQCRB, Complex III subunit 7, QP-C, or Ubiquinol-cytochrome c reductase complex 14 kDa protein is a protein which in humans is encoded by the UQCRB gene. This gene encodes a subunit of the ubiquinol-cytochrome c oxidoreductase complex, which consists of one mitochondrial-encoded and 10 nuclear-encoded subunits. Mutations in this gene are associated with mitochondrial complex III deficiency. Alternatively spliced transcript variants have been found for this gene. Related pseudogenes have been identified on chromosomes 1, 5 and X.
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 gene. UQCRFS1 is a subunit of the respiratory chain protein Ubiquinol Cytochrome c Reductase, which consists of the products of one mitochondrially encoded gene, MTCYTB and ten nuclear genes UQCRC1, UQCRC2, Cytochrome C1, UQCRFS1, UQCRB,UQCRQ, UQCRH, UCRC, and UQCR.
Cytochrome b-c1 complex subunit 6, mitochondrial is a protein that in humans is encoded by the UQCRH gene.
UQCR11 is a protein that in humans is encoded by the UQCR11 gene. UQCR11 is the smallest known component of Complex III in the mitochondrial respiratory chain.
Ubiquinol-cytochrome c reductase, complex III subunit VII, 9.5kDa is a protein that in humans is encoded by the UQCRQ gene. This ubiqinone-binding protein is a subunit of mitochondrial Complex III in the electron transport chain. A mutation in the UQCRQ gene has been shown to cause severe neurological disorders. Infection by Trypanosoma cruzi can cause oxidative modification of this protein in cardiac muscle tissue.
Tetratricopeptide repeat domain 19, also known as TPR repeat protein 19 or Tetratricopeptide repeat protein 19, mitochondrial is a protein that in humans is encoded by the TTC19 gene. This gene encodes a protein with a tetratricopeptide repeat (TPR) domain containing several TPRs of about 34 amino acids each. These repeats are found in a variety of organisms including bacteria, fungi and plants, and are involved in a variety of functions including protein-protein interactions. This protein is embedded in the inner mitochondrial membrane and is involved in the formation of the mitochondrial respiratory chain III. It has also been suggested that this protein plays a role in cytokinesis. Mutations in this gene cause mitochondrial complex III deficiency. Alternatively spliced transcript variants have been found for this gene.
Ubiquinol-cytochrome c reductase complex assembly factor 2 is a protein that in humans is encoded by the UQCC2 gene. Located in the mitochondrial nucleoid, this protein is a complex III assembly factor, playing a role in cytochrome b biogenesis along with the UQCC1 protein. It regulates insulin secretion and mitochondrial ATP production and oxygen consumption. In the sole recorded case, a mutation in the UQCC2 gene caused Complex III deficiency, characterized by intrauterine growth retardation, neonatal lactic acidosis, and renal tubular dysfunction.
LYR motif containing 7, also known as Complex III assembly factor LYRM7 or LYR motif-containing protein 7 is a protein that in humans is encoded by the LYRM7 gene. The protein encoded by this gene is a nuclear-encoded mitochondrial matrix protein that stabilizes UQCRFS1 and chaperones it to the CIII complex. Defects in this gene are a cause of mitochondrial complex III deficiency, nuclear type 8. Three transcript variants encoding two different isoforms have been found for this gene.
(See also: List of proteins in the human body)
Cytochrome c oxidase assembly factor COX14 is a protein that in humans is encoded by the COX14 gene. This gene encodes a small single-pass transmembrane protein that localizes to mitochondria. This protein may play a role in coordinating the early steps of cytochrome c oxidase subunit assembly and, in particular, the synthesis and assembly of the COX I subunit of the holoenzyme. Mutations in this gene have been associated with mitochondrial complex IV deficiency. Alternative splicing results in multiple transcript variants.
