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Nat Commun. 2015 Jun 15;6:7442. doi: 10.1038/ncomms8442.

Fluctuations between multiple EF-G-induced chimeric tRNA states during translocation on the ribosome.

Author information

1
Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Goettingen 37077, Germany.
2
3D Electron Cryomicroscopy Group, Max Planck Institute for Biophysical Chemistry, Goettingen 37077, Germany.

Abstract

The coupled translocation of transfer RNA and messenger RNA through the ribosome entails large-scale structural rearrangements, including step-wise movements of the tRNAs. Recent structural work has visualized intermediates of translocation induced by elongation factor G (EF-G) with tRNAs trapped in chimeric states with respect to 30S and 50S ribosomal subunits. The functional role of the chimeric states is not known. Here we follow the formation of translocation intermediates by single-molecule fluorescence resonance energy transfer. Using EF-G mutants, a non-hydrolysable GTP analogue, and fusidic acid, we interfere with either translocation or EF-G release from the ribosome and identify several rapidly interconverting chimeric tRNA states on the reaction pathway. EF-G engagement prevents backward transitions early in translocation and increases the fraction of ribosomes that rapidly fluctuate between hybrid, chimeric and posttranslocation states. Thus, the engagement of EF-G alters the energetics of translocation towards a flat energy landscape, thereby promoting forward tRNA movement.

PMID:
26072700
PMCID:
PMC4490557
DOI:
10.1038/ncomms8442
[Indexed for MEDLINE]
Free PMC Article

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