Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 111, Issue 42, Pages 15060-15065Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1410873111
Keywords
ribosome; tRNA translocation; viomycin; single-molecule FRET
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Funding
- National Institutes of Health Grant [GM-099719, P30 GM-092424]
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Translocation of mRNA and tRNAs through the ribosome is catalyzed by a universally conserved elongation factor (EF-G in prokaryotes and EF-2 in eukaryotes). Previous studies have suggested that ribosome-bound EF-G undergoes significant structural rearrangements. Here, we follow the movement of domain IV of EF-G, which is critical for the catalysis of translocation, relative to protein S12 of the small ribosomal subunit using single-molecule FRET. We show that ribosome-bound EF-G adopts distinct conformations corresponding to the pre- and posttranslocation states of the ribosome. Our results suggest that, upon ribosomal translocation, domain IV of EF-G moves toward the A site of the small ribosomal subunit and facilitates the movement of peptidyl-tRNA from the A to the P site. We found no evidence of direct coupling between the observed movement of domain IV of EF-G and GTP hydrolysis. In addition, our results suggest that the pretranslocation conformation of the EF-G-ribosome complex is significantly less stable than the posttranslocation conformation. Hence, the structural rearrangement of EF-G makes a considerable energetic contribution to promoting tRNA translocation.
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