The enzyme cytochrome c oxidase or Complex IV, is a large transmembrane protein complex found in bacteria, archaea, and mitochondria of eukaryotes.
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.
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 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 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.
(See also: List of proteins in the human body)
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.
Modern biological research has revealed strong evidence that the enzymes of the mitochondrial respiratory chain assemble into larger, supramolecular structures called supercomplexes, instead of the traditional fluid model of discrete enzymes dispersed in the inner mitochondrial membrane. These supercomplexes are functionally active and necessary for forming stable respiratory complexes.
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.
Cytochrome c oxidase assembly factor 3, also known as Coiled-coil domain-containing protein 56, or Mitochondrial translation regulation assembly intermediate of cytochrome c oxidase protein of 12 kDa is a protein that in humans is encoded by the COA3 gene. This gene encodes a member of the cytochrome c oxidase assembly factor family. Studies of a related gene in fly suggest that the encoded protein is localized to mitochondria and is essential for cytochrome c oxidase function.
Cytochrome c oxidase assembly factor COX20 is a protein that in humans is encoded by the COX20 gene. This gene encodes a protein that plays a role in the assembly of cytochrome c oxidase, an important component of the respiratory pathway. Mutations in this gene can cause mitochondrial complex IV deficiency. There are multiple pseudogenes for this gene. Alternative splicing results in multiple transcript variants.
Cytochrome c oxidase assembly factor 6 is a protein that in humans is encoded by the COA6 gene. Mitochondrial respiratory chain Complex IV, or cytochrome c oxidase, is the component of the respiratory chain that catalyzes the transfer of electrons from intermembrane space cytochrome c to molecular oxygen in the matrix and as a consequence contributes to the proton gradient involved in mitochondrial ATP synthesis. The COA6 gene encodes an assembly factor for mitochondrial complex IV and is a member of the cytochrome c oxidase subunit 6B family. This protein is located in the intermembrane space, associating with SCO2 and COX2. It stabilizes newly formed COX2 and is part of the mitochondrial copper relay system. Mutations in this gene result in fatal infantile cardioencephalomyopathy.
PET117 homolog is a protein that in humans is encoded by the PET117 gene. Localized to mitochondria, this protein is a chaperone protein involved in the assembly of mitochondrial Complex IV, or Cytochrome C Oxidase. Mutations in this gene can cause Complex IV deficiency with symptoms including medulla oblongata lesions and lactic acidosis.
