Seryl-tRNA Synthetases from Methanogenic Archaea: Suppression of Bacterial Amber Mutation and Heterologous Toxicity 

Sonja Lesjak*, Draško Boko and Ivana Weygand–Đurašević

University of Zagreb, Faculty of Science, Department of Chemistry, Horvatovac 102a, HR-10000 Zagreb, Croatia

Article history:

Received July 24, 2009
Accepted March 9, 2010

Key words:

seryl-tRNA synthetase, heterologous toxicity, amber suppression, methanogenic archaea


Methanogenic archaea possess unusual seryl-tRNA synthetases (SerRS), evolutionarily distinct from the SerRSs found in other archaea, eucaryotes and bacteria. Our recent X-ray structural analysis of Methanosarcina barkeri SerRS revealed an idiosyncratic N-terminal domain and catalytic zinc ion in the active site. To shed further light on substrate discrimination by methanogenic-type SerRS, we set up to explore in vivo the interaction of methanogenic- type SerRSs with their cognate tRNAs in Escherichia coli or Saccharomyces cerevisiae. The expression of various methanogenic-type SerRSs was toxic for E. coli, resulting in the synthesis of erroneous proteins, as revealed by β-galactosidase stability assay. Although SerRSs from methanogenic archaea recognize tRNAsSer from all three domains of life in vitro, the toxicity presumably precluded the complementation of endogenous SerRS function in both, E. coli and S. cerevisiae. However, despite the observed toxicity, coexpression of methanogenic-type SerRS with its cognate tRNA suppressed bacterial amber mutation.


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