Journal
EMBO JOURNAL
Volume 29, Issue 18, Pages 3118-3129Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/emboj.2010.192
Keywords
crystal structure; indirect tRNA asparaginylation; transamidosome; transfer-ribonucleoprotein particle; tRNA scaffold
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Funding
- University Louis Pasteur (Strasbourg)
- Centre National de la Recherche Scientifique (CNRS)
- Association pour la Recherche sur le Cancer (ARC)
- ACI Biologie Cellulaire Moleculaire et Structurale
- Center for Carbohydrate Recognition and Signalling (CARB)
- AFM
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Four out of the 22 aminoacyl-tRNAs ( aa-tRNAs) are systematically or alternatively synthesized by an indirect, two-step route requiring an initial mischarging of the tRNA followed by tRNA-dependent conversion of the non-cognate amino acid. During tRNA-dependent asparagine formation, tRNA(Asn) promotes assembly of a ribonucleoprotein particle called transamidosome that allows channelling of the aa-tRNA from non-discriminating aspartyl-tRNA synthetase active site to the GatCAB amidotransferase site. The crystal structure of the Thermus thermophilus transamidosome determined at 3 angstrom resolution reveals a particle formed by two GatCABs, two dimeric ND-AspRSs and four tRNAs(Asn) molecules. In the complex, only two tRNAs are bound in a functional state, whereas the two other ones act as an RNA scaffold enabling release of the asparaginyl-tRNA(Asn) without dissociation of the complex. We propose that the crystal structure represents a transient state of the transamidation reaction. The transamidosome constitutes a transfer-ribonucleoprotein particle in which tRNAs serve the function of both substrate and structural foundation for a large molecular machine.
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