MT-ATP8

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ATP8
Identifiers
Aliases ATP8 , ATPase8, MTMT-ATP synthase F0 subunit 8
External IDs OMIM: 516070 HomoloGene: 124425 GeneCards: ATP8
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

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n/a

RefSeq (protein)

n/a

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Location (UCSC) Chr M: 0.01 – 0.01 Mb n/a
PubMed search [2] n/a
Wikidata
View/Edit Human
Location of the MT-ATP8 gene in the human mitochondrial genome. MT-ATP8 is one of the two ATP synthase mitochondrial genes (red boxes). Map of the human mitochondrial genome.svg
Location of the MT-ATP8 gene in the human mitochondrial genome. MT-ATP8 is one of the two ATP synthase mitochondrial genes (red boxes).
The 46-nucleotide overlap in the reading frames of the human mitochondrial genes MT-ATP8 and MT-ATP6. For each nucleotide triplet (square brackets), the corresponding amino acid is given (one-letter code), either in the +1 frame for MT-ATP8 (in red) or in the +3 frame for MT-ATP6 (in blue). Homo sapiens-mtDNA~NC 012920-ATP8+ATP6 Overlap.svg
The 46-nucleotide overlap in the reading frames of the human mitochondrial genes MT-ATP8 and MT-ATP6. For each nucleotide triplet (square brackets), the corresponding amino acid is given (one-letter code), either in the +1 frame for MT-ATP8 (in red) or in the +3 frame for MT-ATP6 (in blue).
ATP synthase protein 8 (metazoa)
Identifiers
SymbolATP-synt_8
Pfam PF00895
Pfam clan CL0255
InterPro IPR001421
Plant ATP synthase F0 subunit 8
Identifiers
SymbolYMF19
Pfam PF02326
Pfam clan CL0255
InterPro IPR003319
Fungal ATP synthase protein 8 (A6L)
Identifiers
SymbolFun_ATP-synt_8
Pfam PF05933
Pfam clan CL0255
InterPro IPR009230

MT-ATP8 (or ATP8) is a mitochondrial gene with the full name 'mitochondrially encoded ATP synthase membrane subunit 8' that encodes a subunit of mitochondrial ATP synthase, ATP synthase Fo subunit 8 (or subunit A6L). This subunit belongs to the Fo complex of the large, transmembrane F-type ATP synthase. [3] This enzyme, which is also known as complex V, is responsible for the final step of oxidative phosphorylation in the electron transport chain. Specifically, one segment of ATP synthase allows positively charged ions, called protons, to flow across a specialized membrane inside mitochondria. Another segment of the enzyme uses the energy created by this proton flow to convert a molecule called adenosine diphosphate (ADP) to ATP. [4] Subunit 8 differs in sequence between Metazoa, plants and Fungi.

Contents

Structure

The ATP synthase protein 8 of human and other mammals is encoded in the mitochondrial genome by the MT-ATP8 gene. When the complete human mitochondrial genome was first published, the MT-ATP8 gene was described as the unidentified reading frame URF A6L. [3] An unusual feature of the MT-ATP8 gene is its 46-nucleotide overlap with the MT-ATP6 gene. With respect to the reading frame (+1) of MT-ATP8, the MT-ATP6 gene starts on the +3 reading frame.

The MT-ATP8 protein weighs 8 kDa and is composed of 68 amino acids. [5] [6] The protein is a subunit of the F1Fo ATPase, also known as Complex V, which consists of 14 nuclear- and 2 mitochondrial-encoded subunits. F-type ATPases consist of two structural domains, F1 containing the extramembraneous catalytic core and Fo containing the membrane proton channel, linked together by a central stalk and a peripheral stalk. As an A subunit, MT-ATP8 is contained within the non-catalytic, transmembrane Fo portion of the complex, comprising the proton channel. The catalytic portion of mitochondrial ATP synthase consists of 5 different subunits (alpha, beta, gamma, delta, and epsilon) assembled with a stoichiometry of 3 alpha, 3 beta, and a single representative of the other 3. The proton channel consists of three main subunits (a, b, c). This gene encodes the delta subunit of the catalytic core. Alternatively spliced transcript variants encoding the same isoform have been identified. [7] [4]

Function

The MT-ATP8 gene encodes a subunit of mitochondrial ATP synthase, located within the thylakoid membrane and the inner mitochondrial membrane. Mitochondrial ATP synthase catalyzes ATP synthesis, utilizing an electrochemical gradient of protons across the inner membrane during oxidative phosphorylation. [7] The Fo region causes rotation of F1, which has a water-soluble component that hydrolyzes ATP and together, the F1Fo creates a pathway for movement of protons across the membrane. [8]

This protein subunit appears to be an integral component of the stator stalk in yeast mitochondrial F-ATPases. [9] The stator stalk is anchored in the membrane, and acts to prevent futile rotation of the ATPase subunits relative to the rotor during coupled ATP synthesis/hydrolysis. This subunit may have an analogous function in Metazoa.

Nomenclature

The nomenclature of the enzyme has a long history. The F1 fraction derives its name from the term "Fraction 1" and Fo (written as a subscript letter "o", not "zero") derives its name from being the binding fraction for oligomycin, a type of naturally-derived antibiotic that is able to inhibit the Fo unit of ATP synthase. [10] [11] The Fo region of ATP synthase is a proton pore that is embedded in the mitochondrial membrane. It consists of three main subunits A, B, and C, and (in humans) six additional subunits, d, e, f, g, MT-ATP6 (or F6), and MT-ATP8 (or A6L). 3D structure of E. coli homologue of this subunit was modeled based on electron microscopy data (chain M of PDB: 1c17 ). It forms a transmembrane 4-α-bundle.

Clinical Significance

Mutations to MT-ATP8 and other genes affecting oxidative phosphorylation in the mitochondria have been associated with a variety of neurodegenerative and cardiovascular disorders, including mitochondrial complex V deficiency, Leber's hereditary optic neuropathy (LHON), mitochondrial encephalomyopathy with stroke-like episodes (MELAS), Leigh syndrome, and NARP syndrome. Most of the body's cells contain thousands of mitochondria, each with one or more copies of mitochondrial DNA. The severity of some mitochondrial disorders is associated with the percentage of mitochondria in each cell that has a particular genetic change. People with Leigh syndrome due to a MT-ATP6 gene mutation tend to have a very high percentage of mitochondria with the mutation (from more than 90 percent to 95 percent). The less-severe features of NARP result from a lower percentage of mitochondria with the mutation, typically 70 percent to 90 percent. Because these two conditions result from the same genetic changes and can occur in different members of a single family, researchers believe that they may represent a spectrum of overlapping features instead of two distinct syndromes. [4]

Mitochondrial complex V deficiency presents with heterogeneous clinical manifestations including neuropathy, ataxia, hypertrophic cardiomyopathy. Hypertrophic cardiomyopathy can present with negligible to extreme hypertrophy, minimal to extensive fibrosis and myocyte disarray, absent to severe left ventricular outflow tract obstruction, and distinct septal contours/morphologies with extremely varying clinical course. [12] [13]

Mitochondrial complex V deficiency is a shortage (deficiency) or loss of function in complex V of the electron transport chain that can cause a wide variety of signs and symptoms affecting many organs and systems of the body, particularly the nervous system and the heart. The disorder can be life-threatening in infancy or early childhood. Affected individuals may have feeding problems, slow growth, low muscle tone (hypotonia), extreme fatigue (lethargy), and developmental delay. They tend to develop elevated levels of lactic acid in the blood (lactic acidosis), which can cause nausea, vomiting, weakness, and rapid breathing. High levels of ammonia in the blood (hyperammonemia) can also occur in affected individuals, and in some cases result in abnormal brain function (encephalopathy) and damage to other organs. [14] Ataxia, microcephaly, developmental delay and intellectual disability have been observed in patients with a frameshift mutation in MT-ATP6. This causes a C insertion at position 8612 that results in a truncated protein only 36 amino acids long, and two T > C single-nucleotide polymorphisms at positions 8610 and 8614 that result in a homopolymeric cytosine stretch. [15]

Hypertrophic cardiomyopathy, a common feature of mitochondrial complex V deficiency, is characterized by thickening (hypertrophy) of the cardiac muscle that can lead to heart failure. [14] The m.8528T>C mutation occurs in the overlapping region of the MT-ATP6 and MT-ATP8 genes and has been described in multiple patients with infantile cardiomyopathy. This mutation changes the initiation codon in MT-ATP6 to threonine as well as a change from tryptophan to arginine at position 55 of MT-ATP8. [16] [13] Individuals with mitochondrial complex V deficiency may also have a characteristic pattern of facial features, including a high forehead, curved eyebrows, outside corners of the eyes that point downward (downslanting palpebral fissures), a prominent bridge of the nose, low-set ears, thin lips, and a small chin (micrognathia). [14]

Infantile hypertrophic cardiomyopathy (CMHI) is also caused by mutations affecting distinct genetic loci, including MT-ATP6 and MT-ATP8. An infantile form of hypertrophic cardiomyopathy, a heart disorder characterized by ventricular hypertrophy, which is usually asymmetric and often involves the interventricular septum. The symptoms include dyspnea, syncope, collapse, palpitations, and chest pain. They can be readily provoked by exercise. The disorder has inter- and intrafamilial variability ranging from benign to malignant forms with high risk of cardiac failure and sudden cardiac death. [12] [13]

Related Research Articles

ATP synthase Enzyme

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 of P-O bond (phosphodiester bond). The overall reaction catalyzed by ATP synthase is:

MT-ATP6 Mitochondrial protein-coding gene whose product is involved in ATP synthesis

MT-ATP6 is a mitochondrial gene with the full name 'mitochondrially encoded ATP synthase membrane subunit 6' that encodes the ATP synthase Fo subunit 6. This subunit belongs to the Fo complex of the large, transmembrane F-type ATP synthase. This enzyme, which is also known as complex V, is responsible for the final step of oxidative phosphorylation in the electron transport chain. Specifically, one segment of ATP synthase allows positively charged ions, called protons, to flow across a specialized membrane inside mitochondria. Another segment of the enzyme uses the energy created by this proton flow to convert a molecule called adenosine diphosphate (ADP) to ATP. Mutations in the MT-ATP6 gene have been found in approximately 10 to 20 percent of people with Leigh syndrome.

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.

ATP5B

ATP synthase F1 subunit beta, mitochondrial is an enzyme that in humans is encoded by the ATP5F1B gene.

ATP5F1A

ATP synthase F1 subunit alpha, mitochondrial is an enzyme that in humans is encoded by the ATP5F1A gene.

MT-CYB A mitochondrial protein-coding gene whose product is involved in the respiratory chain

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.

ATP5J

ATP synthase-coupling factor 6, mitochondrial is an enzyme subunit that in humans is encoded by the ATP5PF gene.

ATP5G1

The ATP5MC1 gene is one of three human paralogs that encode membrane subunit c of the mitochondrial ATP synthase.

ATP5J2

The ATP5MF gene encodes the ATP synthase subunit f, mitochondrial enzyme in humans.

ATP5L

ATP synthase subunit g, mitochondrial is an enzyme that in humans is encoded by the ATP5MG gene.

ATP5C1

The human ATP5F1C gene encodes the gamma subunit of an enzyme called mitochondrial ATP synthase.

ATP5F1

ATP synthase subunit b, mitochondrial is an enzyme that in humans is encoded by the ATP5PB gene.

ATP5S

ATP synthase subunit s, mitochondrial is an enzyme that in humans is encoded by the ATP5S gene.

ATP5G2

The ATP5MC2 gene is one of three human paralogs that encode membrane subunit c of the mitochondrial ATP synthase.

ATP5I

ATP synthase subunit e, mitochondrial is an enzyme that in humans is encoded by the ATP5ME gene.

ATP5H

The human gene ATP5PD encodes subunit d of the peripheral stalk part of the enzyme mitochondrial ATP synthase.

ATP5D

ATP synthase subunit delta, mitochondrial, also known as ATP synthase F1 subunit delta or F-ATPase delta subunit is an enzyme that in humans is encoded by the ATP5F1D gene. This gene encodes a subunit of mitochondrial ATP synthase. Mitochondrial ATP synthase catalyzes ATP synthesis, utilizing an electrochemical gradient of protons across the inner membrane during oxidative phosphorylation.

ATP5E Protein-coding gene in the species Homo sapiens

ATP synthase F1 subunit epsilon, mitochondrial is an enzyme that in humans is encoded by the ATP5F1E gene. The protein encoded by ATP5F1E is a subunit of ATP synthase, also known as Complex V. Variations of this gene have been associated with mitochondrial complex V deficiency, nuclear 3 (MC5DN3) and Papillary Thyroid Cancer.

ATP5G3

The ATP5MC3 gene is one of three human paralogs that encode membrane subunit c of the mitochondrial ATP synthase.

TMEM70

Transmembrane protein 70 is a protein that in humans is encoded by the TMEM70 gene. It is a transmembrane protein located in the mitochondrial inner membrane involved in the assembly of the F1 and Fo structural subunits of ATP synthase. Mutations in this gene have been associated with neonatal mitochondrial encephalo-cardiomyopathy due to ATP synthase deficiency, causing a wide variety of symptoms including 3-methylglutaconic aciduria, lactic acidosis, mitochondrial myopathy, and cardiomyopathy.

References

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  2. "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
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  4. 1 2 3 "MT-ATP8". Genetics Home Reference. NCBI.
  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. "ATP synthase protein 8". Cardiac Organellar Protein Atlas Knowledgebase (COPaKB).
  7. 1 2 "MT-ATP8 mitochondrially encoded ATP synthase 8 [Homo sapiens (human)]". Gene. NCBI.
  8. Velours J, Paumard P, Soubannier V, Spannagel C, Vaillier J, Arselin G, Graves PV (May 2000). "Organisation of the yeast ATP synthase F(0):a study based on cysteine mutants, thiol modification and cross-linking reagents". Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1458 (2–3): 443–56. doi: 10.1016/S0005-2728(00)00093-1 . PMID   10838057.
  9. Stephens AN, Khan MA, Roucou X, Nagley P, Devenish RJ (May 2003). "The molecular neighborhood of subunit 8 of yeast mitochondrial F1F0-ATP synthase probed by cysteine scanning mutagenesis and chemical modification". The Journal of Biological Chemistry. 278 (20): 17867–75. doi: 10.1074/jbc.M300967200 . PMID   12626501.
  10. Kagawa Y, Racker E (May 1966). "Partial resolution of the enzymes catalyzing oxidative phosphorylation. 8. Properties of a factor conferring oligomycin sensitivity on mitochondrial adenosine triphosphatase". The Journal of Biological Chemistry. 241 (10): 2461–6. doi: 10.1016/S0021-9258(18)96640-8 . PMID   4223640.
  11. Mccarty RE (November 1992). "A PLANT BIOCHEMIST'S VIEW OF H+-ATPases AND ATP SYNTHASES". The Journal of Experimental Biology. 172 (Pt 1): 431–441. doi:10.1242/jeb.172.1.431. PMID   9874753.
  12. 1 2 "MT-ATP8 - ATP synthase protein 8 - Homo sapiens (Human)". www.uniprot.org. UniProt. Retrieved 3 August 2018. CC-BY-icon-80x15.png  This article incorporates text available under the CC BY 4.0 license.
  13. 1 2 3 Ware SM, El-Hassan N, Kahler SG, Zhang Q, Ma YW, Miller E, Wong B, Spicer RL, Craigen WJ, Kozel BA, Grange DK, Wong LJ (May 2009). "Infantile cardiomyopathy caused by a mutation in the overlapping region of mitochondrial ATPase 6 and 8 genes". Journal of Medical Genetics. 46 (5): 308–14. doi:10.1136/jmg.2008.063149. PMID   19188198. S2CID   25354118.
  14. 1 2 3 "Mitochondrial complex V deficiency". Genetics Home Reference. NCBI. Retrieved 3 August 2018.PD-icon.svgThis article incorporates text from this source, which is in the public domain.
  15. Jackson CB, Hahn D, Schröter B, Richter U, Battersby BJ, Schmitt-Mechelke T, Marttinen P, Nuoffer JM, Schaller A (June 2017). "A novel mitochondrial ATP6 frameshift mutation causing isolated complex V deficiency, ataxia and encephalomyopathy". European Journal of Medical Genetics. 60 (6): 345–351. doi:10.1016/j.ejmg.2017.04.006. hdl: 10138/237062 . PMID   28412374.
  16. Imai A, Fujita S, Kishita Y, Kohda M, Tokuzawa Y, Hirata T, Mizuno Y, Harashima H, Nakaya A, Sakata Y, Takeda A, Mori M, Murayama K, Ohtake A, Okazaki Y (March 2016). "Rapidly progressive infantile cardiomyopathy with mitochondrial respiratory chain complex V deficiency due to loss of ATPase 6 and 8 protein". International Journal of Cardiology. 207: 203–5. doi:10.1016/j.ijcard.2016.01.026. PMID   26803244.

Further reading

This article incorporates text from the United States National Library of Medicine, which is in the public domain.

This article incorporates text from the public domain Pfam and InterPro: IPR001421