Correlated conformational events in EF-G and the ribosome regulate translocation

• DOI: 10.1038/nsmb.1925
• Publication Date: 2010-11-08T11:18:36Z
• Authors: James B Munro; Michael R Wasserman; Roger B Altman; Leyi Wang; Scott C Blanchard
• Keywords: Conformational change; Single-molecule FRET; A-site

In bacteria, the translocation of tRNA and mRNA with respect to the ribosome is catalyzed by the conserved GTPase elongation factor-G (EF-G). To probe the rate-determining features in this process, we imaged EF-G-catalyzed translocation from two unique structural perspectives using single-molecule fluorescence resonance energy transfer. The data reveal that the rate at which the ribosome spontaneously achieves a transient, 'unlocked' state is closely correlated with the rate at which the tRNA-like domain IV-V element of EF-G engages the A site. After these structural transitions, translocation occurs comparatively fast, suggesting that conformational processes intrinsic to the ribosome determine the rate of translocation. Experiments conducted in the presence of non-hydrolyzable GTP analogs and specific antibiotics further reveal that allosterically linked conformational events in EF-G and the ribosome mediate rapid, directional substrate movement and EF-G release.