Biology:MT-ND3

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Short description: Mitochondrial protein-coding gene whose product is involved in the respiratory chain


A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example
Location of the MT-ND3 gene in the human mitochondrial genome. MT-ND3 is one of the seven NADH dehydrogenase mitochondrial genes (yellow boxes).

MT-ND3 is a gene of the mitochondrial genome coding for the NADH dehydrogenase 3 (ND3) protein.[1] The ND3 protein is a subunit of NADH dehydrogenase (ubiquinone), which is located in the mitochondrial inner membrane and is the largest of the five complexes of the electron transport chain.[2] Variants of MT-ND3 are associated with Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), Leigh's syndrome (LS) and Leber's hereditary optic neuropathy (LHON).[3][4]

Structure

General features

MT-ND3 is located in human mitochondrial DNA from base pair 10,059 to 10,404.[1] The MT-ND3 gene produces a 13 kDa protein composed of 115 amino acids.[5][6] MT-ND3 is one of seven mitochondrial genes encoding subunits of the enzyme NADH dehydrogenase (ubiquinone), together with MT-ND1, MT-ND2, MT-ND4, MT-ND4L, MT-ND5, and MT-ND6. Also known as Complex I, this enzyme is the largest of the respiratory complexes. The structure is L-shaped with a long, hydrophobic transmembrane domain and a hydrophilic domain for the peripheral arm that includes all the known redox centres and the NADH binding site. The MT-ND3 product and the rest of the mitochondrially encoded subunits are the most hydrophobic of the subunits of Complex I and form the core of the transmembrane region.[2]

Untranslated extra nucleotide

In the MT-ND3 gene from many species of birds and turtles [7] there is an extra nucleotide that is not translated to protein.[8] Translational frameshifting or RNA editing are alternative explanations for maintenance of the functionality of the ND3 reading frame in birds possessing the one-nucleotide insertion. This extra nucleotide feature suggests that turtles might be related to Archosauria, as evidenced by molecular phylogeny studies.[9][10] The absence of the extra nucleotide in crocodilians and some birds and turtles might also indicate that the corresponding taxa have lost this feature.

Function

The MT-ND3 product is a subunit of the respiratory chain Complex I that is believed to belong to the minimal assembly of core proteins required to catalyze NADH dehydrogenation and electron transfer to ubiquinone (coenzyme Q10).[11] Initially, NADH binds to Complex I and transfers two electrons to the isoalloxazine ring of the flavin mononucleotide (FMN) prosthetic arm to form FMNH2. The electrons are transferred through a series of iron-sulfur (Fe-S) clusters in the prosthetic arm and finally to coenzyme Q10 (CoQ), which is reduced to ubiquinol (CoQH2). The flow of electrons changes the redox state of the protein, resulting in a conformational change and pK shift of the ionizable side chain, which pumps four hydrogen ions out of the mitochondrial matrix.[2]

Clinical significance

Pathogenic variants of the mitochondrial gene MT-ND3 are known to cause mtDNA-associated Leigh syndrome, as are variants of MT-ATP6, MT-TL1, MT-TK, MT-TW, MT-TV, MT-ND1, MT-ND2, MT-ND4, MT-ND5, MT-ND6 and MT-CO3. Abnormalities in mitochondrial energy generation result in neurodegenerative disorders like Leigh syndrome, which is characterized by an onset of symptoms between 12 months and three years of age. The symptoms frequently present themselves following a viral infection and include movement disorders and peripheral neuropathy, as well as hypotonia, spasticity and cerebellar ataxia. Roughly half of affected patients die of respiratory or cardiac failure by the age of three. Leigh syndrome is a maternally inherited disorder and its diagnosis is established through genetic testing of the aforementioned mitochondrial genes, including MT-ND3.[3] These complex I genes have been associated with a variety of neurodegenerative disorders, including Leber's hereditary optic neuropathy (LHON), mitochondrial encephalomyopathy with stroke-like episodes (MELAS) and the previously mentioned Leigh syndrome.[4]

Interactions

MT-ND3 has been shown to have 5 binary protein-protein interactions including 2 co-complex interactions. MT-ND3 appears to interact with APP and NDUFA9.[12]

References

  1. ↑ 1.0 1.1 "Entrez Gene: MT-ND3 NADH dehydrogenase subunit 3". https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=4537. 
  2. ↑ 2.0 2.1 2.2 Donald Voet; Judith G. Voet; Charlotte W. Pratt (2013). "18". Fundamentals of biochemistry : life at the molecular level (4th ed.). Hoboken, NJ: Wiley. pp. 581–620. ISBN 9780470547847. 
  3. ↑ 3.0 3.1 "Mitochondrial DNA-Associated Leigh Syndrome and NARP". GeneReviews [Internet]. Seattle (WA): University of Washington, Seattle. 1993–2015. https://www.ncbi.nlm.nih.gov/books/NBK1173. 
  4. ↑ 4.0 4.1 "Association of the mtDNA m.4171C>A/MT-ND1 mutation with both optic neuropathy and bilateral brainstem lesions". BMC Neurology 14: 116. May 2014. doi:10.1186/1471-2377-14-116. PMID 24884847. 
  5. ↑ "Integration of cardiac proteome biology and medicine by a specialized knowledgebase". Circulation Research 113 (9): 1043–53. October 2013. doi:10.1161/CIRCRESAHA.113.301151. PMID 23965338. 
  6. ↑ "NADH-ubiquinone oxidoreductase chain 3". Cardiac Organellar Protein Atlas Knowledgebase (COPaKB). https://amino.heartproteome.org/web/protein/P03897. 
  7. ↑ "Complete mitochondrial genome sequences". http://megasun.bch.umontreal.ca/ogmp/projects/other/mt_list.html. 
  8. ↑ "An extra nucleotide is not translated in mitochondrial ND3 of some birds and turtles". Molecular Biology and Evolution 15 (11): 1568–71. November 1998. doi:10.1093/oxfordjournals.molbev.a025884. PMID 12572620. 
  9. ↑ "Phylogenomic analyses support the position of turtles as the sister group of birds and crocodiles (Archosauria)". BMC Biology 10: 65. July 2012. doi:10.1186/1741-7007-10-65. PMID 22839781. 
  10. ↑ "More than 1000 ultraconserved elements provide evidence that turtles are the sister group of archosaurs". Biology Letters 8 (5): 783–6. October 2012. doi:10.1098/rsbl.2012.0331. PMID 22593086. 
  11. ↑ "MT-ND3 - NADH-ubiquinone oxidoreductase chain 3 - Homo sapiens (Human)". The UniProt Consortium. https://www.uniprot.org/uniprot/P03897. 
  12. ↑ "5 binary interactions found for search term MT-ND3". IntAct Molecular Interaction Database. EMBL-EBI. https://www.ebi.ac.uk/intact/interactions?conversationContext=3&query=MT-ND3. 

Further reading

External links



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