engleski

Structure, function and evolution of aminoacyl-tRNA synthetases

OBJECTIVES: The aminoacyl-tRNA synthetases are large family of house-keeping enzymes essential for translation of genetic information. In eukaryotic cells they are found in cytosol and in all protein-synthesizing organelles. The availability of many genomic sequences, obtained in the course of genome sequencing projects, enabled us to clone the genes encoding serine specific aminoacyl-tRNA synthetases (SerRS) from different taxonomic domains and to investigate the interaction of these enzymes with their cognate substrates through evolution. METHODS: SerRS genes were cloned either by screening of relevant libraries or by PCR amplification of known sequences. Series of mutants were generated by site-directed mutagenesis, the genes were overexpressed and mutant proteins purified. Functional tRNAs were prepared by in vitro transcription of synthetic tRNA genes. The recognition of substrates by mutant synthetases were studied by combination of in vivo and in vitro approaches. RESULTS and CONCLUSIONS: Mutational analysis followed by biochemical characterization of numerous altered forms of the seryl-tRNA synthetases, revealed structural resemblance among these proteins, especially in the active site. However, subtle structural differences are prominent among bacterial, and eukaryotic organellar or cytosolic SerRS. Consequently, these enzymes exhibit different mode of recognition of common substrates and show unequal sensitivity to competitive inhibitors, which are often substrate analogues. This divergence between bacterial and eukaryotic enzyme homologues, together with their essential role in protein synthesis, makes aminoacyl-tRNA synthetases excellent targets for the development of selectively acting antibacterial agents.

aminoacyl-tRNA synthetase

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