engleski

Archaeal aminoacyl-tRNA synthetases interact with the ribosome to recycle tRNAs

Aminoacyl-tRNA synthetases (aaRS) are essential enzymes catalyzing the formation of aminoacyl- tRNAs (aa-tRNAs), the immediate precursors for encoded peptides in ribosomal protein synthesis. Previous studies have suggested a link between tRNA aminoacylation and high- molecular-weight cellular complexes such as the cytoskeleton or ribosomes. However, the structural basis of these interactions and potential mechanistic implications are not well understood. To biochemically characterize these interactions we have used a system of two interacting archaeal aaRSs ; an atypical methanogenic type SerRS (mSerRS) and an archaeal ArgRS. We have shown that these two aaRSs bind to the large ribosomal subunit with micromolar affinities. More specifically, we identify the L7/L12 stalk and the proteins located near the stalk base as the main sites for aaRS binding. Finally, we have performed a bioinformatics analysis of synonymous codons in the Methanothermobacter thermautotrophicus genome that supports a mechanism in which the deacylated tRNAs may be recharged by aaRSs bound to the ribosome and reused at the next occurrence of a codon encoding the same amino acid. These results suggest a mechanism of tRNA recycling in which aaRSs associate with the L7/L12 stalk region of the ribosome to recapture the tRNAs released from the preceeding ribosome in polysomes.

aminoacyl-tRNA synthetase ; protein complex ; ribosome ; tRNA ; SPR ; thermophoresis

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