engleski

Improving substrate quality control by aminoacyl- tRNA synthetase complex formation

Aminoacyl-tRNA synthetases (aaRS) are well known to interact with other cellular proteins. In the archaeon Methanothermobacter thermautotrophicus a complex is formed by the transient gathering of the arginyl- and seryl-tRNA synthetase (ArgRS and SerRS). Pull-down and surface plasmon resonance experiments with truncated ArgRS variants showed that the N-terminal part of ArgRS serves as the recognition platform for SerRS, with emphasis on the elements involved in tRNAArg recognition. The shortened variants Δ89-ArgRS and ΔNtot-ArgRS show decreased ability for cognate tRNA binding and charging. Regarding the possible effect that reaction precursors may have on the stability of ArgRS:SerRS complex, it is shown that the SerRS substrates exert no influence. Furthermore, tRNASer is able to participate in ternary [SerRS:tRNASer]:ArgRS complex formation with a stability comparable to that of the binary SerRS:ArgRS assembly. In contrast, interaction of these proteins is susceptible to the addition of fully modified tRNAArg transcript which ultimately leads to dissociation of the complex. Overexpression of tRNAArg in E. coli cells results with the production of three distinct molecular species which differ in the amount of added posttranscriptional modifications. Arginyl-tRNA synthetase investigated in this work aminoacylates such substrates with comparable efficacy. Interestingly, SerRS is able to inhibit arginylation of poorer substrates, i.e., less modified tRNAArg molecules. Elimination of the partly modified tRNAs from the translation process shows how this protein complex may act as a safeguarding switch improving decoding accuracy.

aminoacyl-tRNA synthetase complexes; translational accuracy; protein-protein interactions; posttranscriptional modifications; tRNA

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