Roy H, Becker HD, Reinbolt J, Kern D

Departement Mecanismes et Macromolecules de la Synthese Proteique et Cristallogenese, UPR 9002, Institut de Biologie Moleculaire et Cellulaire du Centre National de la Recherche Scientifique, 15 Rue Rene Descartes, F-67084 Strasbourg Cedex, France.

Faithful protein synthesis relies on a family of essential enzymes called aminoacyl-tRNA synthetases, assembled in a piecewise fashion. Analysis of the completed archaeal genomes reveals that all archaea that possess asparaginyl-tRNA synthetase (AsnRS) also display a second ORF encoding an AsnRS truncated from its anticodon binding-domain (AsnRS2). We show herein that Pyrococcus abyssi AsnRS2, in contrast to AsnRS, does not sustain asparaginyl-tRNAAsn synthesis but is instead capable of converting aspartic acid into asparagine. Functional analysis and complementation of an Escherichia coli asparagine auxotrophic strain show that AsnRS2 constitutes the archaeal homologue of the bacterial ammonia-dependent asparagine synthetase A (AS-A), therefore named archaeal asparagine synthetase A (AS-AR). Primary sequence- and 3D-based phylogeny shows that an archaeal AspRS ancestor originated AS-AR, which was subsequently transferred into bacteria by lateral gene transfer in which it underwent structural changes producing AS-A. This study provides evidence that a contemporary aminoacyl-tRNA synthetase can be recruited to sustain amino acid metabolism.

Mesh Terms:
Amino Acid Sequence, Amino Acids, Amino Acyl-tRNA Synthetases, Aspartate-tRNA Ligase, Catalytic Domain, Cloning, Molecular, Escherichia coli, Genes, Archaeal, Genes, Bacterial, Models, Molecular, Molecular Sequence Data, Phylogeny, Protein Conformation, Pyrococcus, RNA, Transfer, Amino Acyl, Sequence Homology, Amino Acid, Substrate Specificity

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174066

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