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Biochem Soc Trans. 2011 Apr;39(2):658-62. doi: 10.1042/BST0390658.

The ribosome as a molecular machine: the mechanism of tRNA-mRNA movement in translocation.

Author information

1
Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany. rodnina@uni-wh.de

Abstract

Translocation of tRNA and mRNA through the ribosome is one of the most dynamic events during protein synthesis. In the cell, translocation is catalysed by EF-G (elongation factor G) and driven by GTP hydrolysis. Major unresolved questions are: how the movement is induced and what the moving parts of the ribosome are. Recent progress in time-resolved cryoelectron microscopy revealed trajectories of tRNA movement through the ribosome. Driven by thermal fluctuations, the ribosome spontaneously samples a large number of conformational states. The spontaneous movement of tRNAs through the ribosome is loosely coupled to the motions within the ribosome. EF-G stabilizes conformational states prone to translocation and promotes a conformational rearrangement of the ribosome (unlocking) that accelerates the rate-limiting step of translocation: the movement of the tRNA anticodons on the small ribosomal subunit. EF-G acts as a Brownian ratchet providing directional bias for movement at the cost of GTP hydrolysis.

PMID:
21428957
DOI:
10.1042/BST0390658
[Indexed for MEDLINE]

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