MT-CYB

Last updated
CYTB
Identifiers
Aliases CYTB , MTCYB, MT-CYB, cytochrome b
External IDs OMIM: 516020 MGI: 102501 HomoloGene: 5013 GeneCards: CYTB
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

n/a

n/a

RefSeq (protein)

n/a

NP_904340

Location (UCSC)n/a Chr M: 0.01 – 0.02 Mb
PubMed search [2] [3]
Wikidata
View/Edit Human View/Edit Mouse
Location of the MT-CYB gene in the human mitochondrial genome (coral box). Map of the human mitochondrial genome.svg
Location of the MT-CYB gene in the human mitochondrial genome (coral box).

Cytochrome b is a protein that in humans is encoded by the MT-CYB gene. [4] Its gene product is a subunit of the respiratory chain protein Ubiquinol Cytochrome c Reductase (UQCR, Complex III or Cytochrome bc1 complex), which consists of the products of one mitochondrially encoded gene, MT-CYB (mitochondrial cytochrome b) and ten nuclear genes: UQCRC1 , UQCRC2 , Cytochrome c1 , UQCRFS1 (Rieske protein), UQCRB , "11kDa protein", UQCRH (cyt c1 Hinge protein), Rieske Protein presequence, "cyt. c1 associated protein", and Rieske-associated protein.

Contents

Structure

The MT-CYB gene is located on the p arm of mitochondrial DNA in position 12 and spans 1,140 base pairs. [4] The gene produces a 42.7 kDa protein named cytochrome b composed of 380 amino acids. [5] [6] Cytochrome b is an integral membrane protein with hydrophobic properties. The catalytic core of the enzyme is composed of eight transmembrane helices, the iron-sulfur protein, and cytochrome c1. [7] Cytochrome b is a fundamental component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex) that is part of the mitochondrial respiratory chain. The b-c1 complex mediates electron transfer from ubiquinol to cytochrome c. [8] The structure of the complex is a symmetric homodimer. It is composed of eleven structural subunits, including one mitochondrial genome encoded cytochrome b and ten other nucleus encoded subunits. These subunits include three respiratory subunits (MT-CYB, CYC1 and UQCRFS1), two core proteins (UQCRC1 and UQCRC2) and six low-molecular weight proteins (UQCRH/QCR6, UQCRB/QCR7, UQCRQ/QCR8, UQCR10/QCR9, UQCR11/QCR10 and a cleavage product of UQCRFS1). The total molecular mass of the complex is about 450 kDa. [9] [8]

Function

The mitochondrial cytochrome b is fundamental for the assembly and function of Complex III of the mitochondrial respiratory chain. [10] Complex III is responsible for the catalysis of electron transfer from coenzyme Q to cytochrome c in the mitochondrial respiratory chain by translocating protons concomitantly across the inner membrane of the mitochondria. [11] [8] The transfer of electrons then contributes to the generation of a proton gradient across the mitochondrial membrane that is then used for ATP synthesis. [8]

Clinical significance

Mutations in MT-CYB can result in mitochondrial deficiencies and associated disorders. It is majorly associated with a complex III deficiency, a deficiency in an enzyme complex which catalyzes electron transfer from coenzyme Q to cytochrome c in the mitochondrial respiratory chain. A complex III deficiency can result in a highly variable phenotype depending on which tissues are affected. [8] Most frequent clinical manifestations include progressive exercise intolerance and cardiomyopathy. Occasional multisystem disorders accompanied by exercise intolerance may arise as well, in forms of deafness, mental retardation, retinitis pigmentosa, cataract, growth retardation, and epilepsy. [8] Other phenotypes include mitochondrial encephalomyopathy, mitochondrial myopathy, Leber hereditary optic neuropathy, muscle weakness, myoglobinuria, blood acidosis, renal tubulopathy, and more. [8] [9] Complex III deficiency is known to be rare among mitochondrial diseases and may follow a maternal or mendelian mode of inheritance due to its duality of genetic origin. [7]

Related Research Articles

Coenzyme Q – cytochrome c reductase

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 C1 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 cytochrome c in the mitochondrial respiratory chain. It is formed in the cytosol and targeted to the mitochondrial intermembrane space. Cytochrome c1 belongs to the cytochrome c family of proteins.

Cytochrome b A mitochondrial protein involved in the respiratory chain

Cytochrome b 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 subunit I Enzyme of the respiratory chain encoded by the mitochondrial genome

Cytochrome c oxidase I (COX1) also known as mitochondrially encoded cytochrome c oxidase I (MT-CO1) is a protein that in humans is encoded by the MT-CO1 gene. In other eukaryotes, the gene is called COX1, CO1, or COI. Cytochrome c oxidase I is the main subunit of the cytochrome c oxidase complex. Mutations in MT-CO1 have been associated with Leber's hereditary optic neuropathy (LHON), acquired idiopathic sideroblastic anemia, Complex IV deficiency, colorectal cancer, sensorineural deafness, and recurrent myoglobinuria.

Cytochrome c oxidase subunit II Enzyme of the respiratory chain encoded by the mitochondrial genome

Cytochrome c oxidase subunit 2, also known as cytochrome c oxidase polypeptide II, is a protein that in humans 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 Enzyme of the respiratory chain encoded by the mitochondrial genome

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. Cytochrome c oxidase subunit III is also one of the three mitochondrial DNA (mtDNA) encoded subunits of respiratory complex IV. Variants of MT-CO3 have been associated with isolated myopathy, severe encephalomyopathy, Leber hereditary optic neuropathy, mitochondrial complex IV deficiency, and recurrent myoglobinuria.

CYC1

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.

UQCRC1

Cytochrome b-c1 complex subunit 1, mitochondrial is a protein that in humans is encoded by the UQCRC1 gene.

BCS1L

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.

COX6B1

Cytochrome c oxidase subunit 6B1 is an enzyme that in humans is encoded by the COX6B1 gene. Cytochrome c oxidase 6B1 is a subunit of the cytochrome c oxidase complex, also known as Complex IV, the last enzyme in the mitochondrial electron transport chain. Mutations of the COX6B1 gene are associated with severe infantile encephalomyopathy and mitochondrial complex IV deficiency (MT-C4D).

UCRC

Ubiquinol-cytochrome c reductase complex , also known as UCRC or UQCR10, is a human gene.

UQCRB

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.

UQCRC2

Cytochrome b-c1 complex subunit 2, mitochondrial (UQCRC2), also known as QCR2, UQCR2, or MC3DN5 is a protein that in humans is encoded by the UQCRC2 gene. The product of UQCRC2 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, "11kDa protein", UQCRH, Rieske Protein presequence, "cyt. c1 associated protein", and "Rieske-associated protein." Defects in UQCRC2 are associated with mitochondrial complex III deficiency, nuclear, type 5.

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 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.

UQCRH

Cytochrome b-c1 complex subunit 6, mitochondrial is a protein that in humans is encoded by the UQCRH gene.

Mitochondrially encoded tRNA leucine 2 (CUN) also known as MT-TL2 is a transfer RNA which in humans is encoded by the mitochondrial MT-TL2 gene.

Mitochondrially encoded tRNA asparagine also known as MT-TN is a transfer RNA which in humans is encoded by the mitochondrial MT-TN gene.

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.

UQCC2

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.

References

  1. 1 2 3 GRCm38: Ensembl release 89: ENSMUSG00000064370 - Ensembl, May 2017
  2. "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  3. "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. 1 2 "Entrez Gene: CYTB cytochrome b".
  5. Zong NC, Li H, Li H, Lam MP, Jimenez RC, Kim CS, Deng N, Kim AK, Choi JH, Zelaya I, Liem D, Meyer D, Odeberg J, Fang C, Lu HJ, Xu T, Weiss J, Duan H, Uhlen M, Yates JR, Apweiler R, Ge J, Hermjakob H, Ping P (Oct 2013). "Integration of cardiac proteome biology and medicine by a specialized knowledgebase". Circulation Research. 113 (9): 1043–53. doi:10.1161/CIRCRESAHA.113.301151. PMC   4076475 . PMID   23965338.
  6. "cytochrome b". Cardiac Organellar Protein Atlas Knowledgebase (COPaKB).
  7. 1 2 Fragaki K, Procaccio V, Bannwarth S, Serre V, O'Hearn S, Potluri P, Augé G, Casagrande F, Caruba C, Lambert JC, Paquis-Flucklinger V (September 2009). "A neonatal polyvisceral failure linked to a de novo homoplasmic mutation in the mitochondrially encoded cytochrome b gene". Mitochondrion. 9 (5): 346–52. doi:10.1016/j.mito.2009.06.002. PMID   19563916.
  8. 1 2 3 4 5 6 7 "UniProtKB - P00156 (CYB_HUMAN)". The UniProt Consortium.
  9. 1 2 Gil Borlado MC, Moreno Lastres D, Gonzalez Hoyuela M, Moran M, Blazquez A, Pello R, Marin Buera L, Gabaldon T, Garcia Peñas JJ, Martín MA, Arenas J, Ugalde C (September 2010). "Impact of the mitochondrial genetic background in complex III deficiency". PLOS ONE. 5 (9): e12801. Bibcode:2010PLoSO...512801G. CiteSeerX   10.1.1.350.7243 . doi:10.1371/journal.pone.0012801. PMC   2941448 . PMID   20862300.
  10. Massie R, Wong LJ, Milone M (July 2010). "Exercise intolerance due to cytochrome b mutation". Muscle & Nerve. 42 (1): 136–40. doi:10.1002/mus.21649. PMID   20544923.
  11. Baum H, Rieske JS, Silman HI, Lipton SH (March 1967). "On the mechanism of electron transfer in complex iii of the electron transfer chain". Proceedings of the National Academy of Sciences of the United States of America. 57 (3): 798–805. Bibcode:1967PNAS...57..798B. doi:10.1073/pnas.57.3.798. PMC   335578 . PMID   16591533.

Further reading