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mitochondrially encoded tRNA threonine
Alt. symbolsMTTT
NCBI gene4576
Other data
LocusChr. MT [1]

Mitochondrially encoded tRNA threonine also known as MT-TT is a transfer RNA which in humans is encoded by the mitochondrial MT-TT gene.[1]


The MT-TT gene is located on the p arm of the non-nuclear mitochondrial DNA at position 12 and it spans 66 base pairs.[2] The structure of a tRNA molecule is a distinctive folded structure which contains three hairpin loops and resembles a three-leafed clover.[3]


MT-TT is a small 66 nucleotide RNA (human mitochondrial map position 15888-15953) that transfers the amino acid threonine to a growing polypeptide chain at the ribosome site of protein synthesis during translation.

Clinical significance

Myoclonic epilepsy with ragged-red fibers (MERRF)

Mutations in MT-TT have been associated with myoclonic epilepsy with ragged-red fibers (MERRF), and cause mitochondrial energy deficiencies and reduced proliferation leading to oxidative phosphorylation. Myoclonic epilepsy with ragged-red fibers (MERRF) is a rare mitochondrial disorder that affects many parts of the body, particularly the muscles and nervous system. In most cases, the signs and symptoms of this disorder appear during childhood or adolescence. The features of MERRF vary widely among affected individuals, even among members of the same family. Common clinical manifestations include myoclonus, myopathy, spasticity, epilepsy, peripheral neuropathy, dementia, ataxia, atrophy and more.[4][5] In addition, mutations have also been linked to lethal infantile mitochondrial myopathy, Parkinson's disease associated with a 15950G>A mutation,[6] and a 15923A>G mutation found to result in an unconfirmed heart disease.[7][8]

Cytochrome c oxidase deficiency

MT-TT mutations result in complex IV deficiency of the mitochondrial respiratory chain, also known as the cytochrome c oxidase deficiency. Cytochrome c oxidase deficiency is a rare genetic condition that can affect multiple parts of the body, including skeletal muscles, the heart, the brain, or the liver. Common clinical manifestations include myopathy, hypotonia, and encephalomyopathy, lactic acidosis, and hypertrophic cardiomyopathy.[9] A 15915G>A mutation was found in a patient with cytochrome c oxidase deficiency with accompany symptoms of seizures, progressive hearing loss and muscle weakness.[10]


  1. ^ Anderson S, Bankier AT, Barrell BG, de Bruijn MH, Coulson AR, Drouin J, Eperon IC, Nierlich DP, Roe BA, Sanger F, Schreier PH, Smith AJ, Staden R, Young IG (April 1981). "Sequence and organization of the human mitochondrial genome". Nature. 290 (5806): 457–65. doi:10.1038/290457a0. PMID 7219534.
  2. ^ "MT-TT mitochondrially encoded tRNA threonine [Homo sapiens (human)] - Gene - NCBI".
  3. ^ "tRNA / transfer RNA". Learn Science at Scitable.
  4. ^ "Myoclonic epilepsy with ragged-red fibers". Genetics Home Reference. U.S. National Library of Medicine.
  5. ^ Graham BH, Waymire KG, Cottrell B, Trounce IA, MacGregor GR, Wallace DC (July 1997). "A mouse model for mitochondrial myopathy and cardiomyopathy resulting from a deficiency in the heart/muscle isoform of the adenine nucleotide translocator". Nature Genetics. 16 (3): 226–34. doi:10.1038/ng0797-226. PMID 9207786.
  6. ^ Grasbon-Frodl EM, Kösel S, Sprinzl M, von Eitzen U, Mehraein P, Graeber MB (April 1999). "Two novel point mutations of mitochondrial tRNA genes in histologically confirmed Parkinson disease". Neurogenetics. 2 (2): 121–7. doi:10.1007/s100480050063. PMID 10369889.
  7. ^ Yoon KL, Aprille JR, Ernst SG (May 1991). "Mitochondrial tRNA(thr) mutation in fatal infantile respiratory enzyme deficiency". Biochemical and Biophysical Research Communications. 176 (3): 1112–5. doi:10.1016/0006-291X(91)90399-R. PMID 1645537.
  8. ^ Reference, Genetics Home. "MT-TT gene". Genetics Home Reference.
  9. ^ Reference, Genetics Home. "Cytochrome c oxidase deficiency". Genetics Home Reference. This article incorporates text from this source, which is in the public domain.
  10. ^ Nishino I, Seki A, Maegaki Y, Takeshita K, Horai S, Nonaka I, Goto Y (August 1996). "A novel mutation in the mitochondrial tRNA(Thr) gene associated with a mitochondrial encephalomyopathy". Biochemical and Biophysical Research Communications. 225 (1): 180–5. doi:10.1006/bbrc.1996.1150. PMID 8769114.

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