An aminoacyl-tRNA synthetase:elongation factor complex for substrate channeling in archaeal translation

Translation requires the specific attachment of amino acids to tRNAs by aminoacyl-tRNA synthetases (aaRSs) and the subsequent delivery of aminoacyl-tRNAs to the ribosome by elongation factor 1 alpha (EF-1a). Interactions between EF-1a and various aaRSs have been described in eukaryotes, but the role of these complexes remains unclear. To investigate possible interactions between EF-1a and other cellular components, a yeast two-hybrid screen was performed for the archaeon Methanothermobacter thermautotrophicus. EF-1a was found to form a stable complex with leucyl-tRNA synthetase (LeuRS; KD=0.7kM). Complex formation had little effect on EF-1a activity, but increased the kcat for Leu-tRNA Leu synthesis »8-fold. In addition, EF-1a co-purified with the archaeal multi-synthetase complex (MSC) comprised of LeuRS, LysRS and ProRS, suggesting the existence of a larger aaRS:EF-1a complex in archaea. These interactions between EF-1a and the archaeal MSC contribute to translational fidelity both by enhancing the aminoacylation efficiencies of the three aaRSs in the complex and by coupling two stages of translation: aminoacylation of cognate tRNAs and their subsequent channeling to the ribosome.