Yeast cytoplasmic and mitochondrial methionyl-tRNA synthetases: Two structural frameworks for identical functions

Bruno Senger, Laurence Despons, Philippe Walter, Hieronim Jakubowski, Franco Fasiolo

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


The yeast Saccharomyces cerevisiae possesses two methionyl-tRNA synthetases (MetRS), one in the cytoplasm and the other in mitochondria. The cytoplasmic MetRS has a zinc-finger motif of the type Cys-X2-Cys-X9-Cys-X2-Cys in an insertion domain that divides the nucleotide-binding fold into two halves, whereas no such motif is present in the mitochondrial MetRS. Here, we show that tightly bound zinc atom is present in the cytoplasmic MetRS but not in the mitochondrial MetRS. To test whether the presence of a zinc-binding site is required for cytoplasmic functions of MetRS, we constructed a yeast strain in which cytoplasmic MetRS gene was inactivated and the mitochondrial MetRS gene was expressed in the cytoplasm. Provided that methionine-accepting tRNA is overexpressed, this strain was viable, indicating that mitochondrial MetRS was able to aminoacylate tRNAMet in the cytoplasm. Site-directed mutagenesis demonstrated that the zinc domain was required for the stability and consequently for the activity of cytoplasmic MetRS. Mitochondrial MetRS, like cytoplasmic MetRS, supported homocysteine editing in vivo in the yeast cytoplasm. Both MetRSs catalyzed homocysteine editing and aminoacylation of coenzyme A in vitro. Thus, identical synthetic and editing functions can be carried out in different structural frameworks of cytoplasmic and mitochondrial MetRSs.

Original languageEnglish (US)
Pages (from-to)205-216
Number of pages12
JournalJournal of molecular biology
Issue number1
StatePublished - Aug 3 2001

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Structural Biology
  • Molecular Biology


  • Homocysteine editing
  • Methionyl-S-coenzyme A
  • Methionyl-tRNA synthetase
  • Yeast
  • Zinc


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