Transfer RNA-mediated regulation of ribosome dynamics during protein synthesis

Translocation of transfer RNAs (tRNAs) through the ribosome during protein synthesis involves large-scale structural rearrangements of the ribosome and the ribosome-bound tRNAs that are accompanied by extensive and dynamic remodeling of tRNA-ribosome interactions. The contributions that rearranging individual tRNA-ribosome interactions make to directing tRNA movements during translocation, however, remain largely unknown. To address this question, we have used single-molecule fluorescence resonance energy transfer to characterize the dynamics of ribosomal pre-translocation (PRE) complex analogs carrying either wild-type or systematically mutagenized tRNAs. Our data reveal how specific tRNA-ribosome interactions regulate the rate with which the PRE complex rearranges into a critical, on-pathway translocation intermediate and how these interactions control the stability of the resulting configuration. More interestingly, our results suggest that the conformational flexibility of the tRNA molecule itself plays a crucial role in directing the structural dynamics of the PRE complex during translocation.