Initiation codons in mammalian mitochondria: differences in genetic code in the organelle

Biochemistry. 1987 Dec 15;26(25):8247-51. doi: 10.1021/bi00399a034.


The bovine mitochondrial gene products ND2 and ND4, components of NADH dehydrogenase, have been purified from a chloroform/methanol extract of mitochondrial membranes, and the human mitochondrial gene products ND2 and cytochrome b have been obtained by similar procedures. They have been identified by comparison of their amino-terminal protein sequences with those predicted from DNA sequences of bovine and human mitochondrial DNA. All of the proteins have methionine as their amino-terminal residue. In bovine ND2, this residue is encoded by the "universal" isoleucine codon AUA, and the sequences of human cytochrome b and bovine ND2 demonstrate that AUA also encodes methionine in the elongation step of mitochondrial protein synthesis. In human ND2, the amino-terminal methionine is encoded by AUU, which, as in the "universal" genetic code, is also used as an isoleucine codon in elongation. Thus, AUU has a dual coding function which is dependent upon its context.

MeSH terms

  • Adenosine Triphosphatases / genetics*
  • Adenosine Triphosphatases / isolation & purification
  • Amino Acids / analysis
  • Animals
  • Cattle
  • Codon*
  • Cytochrome Reductases / genetics*
  • Cytochrome b Group / genetics*
  • Cytochrome b Group / isolation & purification
  • DNA, Mitochondrial / genetics*
  • Female
  • Genes*
  • Humans
  • Macromolecular Substances
  • Mitochondria / enzymology*
  • Mitochondria, Heart / enzymology*
  • Molecular Weight
  • NADH Dehydrogenase / genetics*
  • NADH Dehydrogenase / isolation & purification
  • Placenta / enzymology
  • RNA, Messenger*
  • Submitochondrial Particles / enzymology


  • Amino Acids
  • Codon
  • Cytochrome b Group
  • DNA, Mitochondrial
  • Macromolecular Substances
  • RNA, Messenger
  • Cytochrome Reductases
  • NADH Dehydrogenase
  • Adenosine Triphosphatases