Ribosomes are complex molecular machines that process genetic information into protein products essential for life. At the heart of ribosome function is the ability to accurately select tRNAs carrying appropriate amino acids and move (translocate) them in exact frame with the codon messages occurring in mRNA. This translocation process demands that the large and small ribosomal subunits communicate in an exacting way to move the message and growing nascent peptide chain to a fruitful endpoint. We propose to study the effect of EF-G on this process, using rapid non-equilibrium probing (RNP), in conjunction with other biochemical approaches, to identify the time-dependent alterations occurring in rRNA as EF-G is added and is structurally modified in the translocation process. The model proposed is that EF-G acts in an escapement capacity, synchronizing the movement of the tRNAs with that of mRNA. By analyzing changes in solvent accessibility that occur in specific regions of 16S and 23S rRNA, we will be to identify the time- correlated events of the translocation process. This proposal is high risk since there are no detailed kinetic studies on the activities of EF-G on the ribosome. However, the impact is great, since if this scenario proves to be correct, it will allow us to understand how such synchronous movements take place on the ribosome, which in turn will provide insight on similar coordinated processes in other systems.
| Tanner, Douglas R; Hedrick, Emily G; Hill, Walter E (2012) Real-time evidence for EF-G-induced dynamics of helix 44 in 16S rRNA. J Mol Biol 422:45-57 |
