Book of Abstracts: Albany 2005
Mechanism for the Disassembly of the Post-termination Complex Inferred from Cryo-EM Studies
Ribosome recycling, the disassembly of the post-termination complex after each round of protein synthesis, is an essential step in messenger RNA translation, but its mechanism has remained obscure. In eubacteria, recycling is catalyzed by RRF (ribosome recycling factor) and EF-G (elongation factor G). By using cryo-electron microscopy, we have obtained two density maps, one of the RRF-bound post-termination complex and one of the 50S subunit bound with both EF-G and RRF. Comparing the two maps, we found domain I of RRF to remain in the same orientation, while domain II has undergone a large rotation (∼60 degrees) upon interaction with EF-G on the 50S subunit. Mapping this movement onto the 70S post-termination complex reveals that it will result in a disruption of the inter-subunit bridges B2a (h44:H69) and B3 (h44:H71), thus effecting a separation of the two subunits. These observations provide the structural basis for the mechanism by which the post-termination complex is split into subunits by the joint action of RRF and EF-G.
1Department of Biomedical Sciences