Book of Abstracts: Albany 2007
June 19-23 2007
Specific Interactions of Elongation Factor-G and Ribosome Recycling Factor on the 50S Subunit Revealed by Cryo-EM
In prokaryotes, after each round of protein synthesis, the 70S ribosome needs to be disassembled before entering another cycle of translation. This process, termed as ribosome recycling, is facilitated by three ribosomal factors, elongation factor-G (EF-G), ribosome recycling factor (RRF), and initiation factor 3 (IF3). Previously, by using cryo-EM technique, we have demonstrated that an inter-domain rotation of RRF, caused by the binding of EF-G, is responsible for the major event of ribosome recycling, the splitting of the 70S ribosome [Gao, N. et al. Mol Cell 18, 663-674 (2005).]. To further understand the structural basis of this EF-G-facilitated inter-domain movement of RRF, in present work, we present a quasi-atomic model for the interaction between EF-G and RRF on the 50S subunit. This model is derived by real-space refinement of X-ray structures into a 9 Å (FSC at 0.5 cutoff) cryo-EM map of a 50S·EFG·GDPNP·RRF complex. Structural analysis based on this model suggests that three domains of EF-G (III-V) are directly involved in this inter-domain movement, and attributes different roles for the three domains in this process. The specific interactions revealed on the inter-molecule interfaces provide a structural basis of the EF-G-triggered rotation of RRF head domain, and serve a framework for future mutational study. More importantly, a comparative analysis of the EF-G conformation in this model with other known conformations provides some clues regarding the mechanism of the conformational signal transduction on EF-G, which translates the GTP hydrolysis signal into the inter-domain rearrangement of EF-G.
1Howard Hughes Medical Institute