Spontaneous reverse movement of mRNA-bound tRNA through the ribosome
| Autor: | Holger Stark, Marina V. Rodnina, Yuri P. Semenkov, Niels Fischer, Andrey L. Konevega, Wolfgang Wintermeyer |
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| Rok vydání: | 2007 |
| Předmět: |
Models
Molecular Messenger RNA Movement Cryoelectron Microscopy RNA Transfer Amino Acyl Biology Ribosome Elongation factor RNA Bacterial A-site RNA Transfer Biochemistry Structural Biology Protein Biosynthesis Transfer RNA Escherichia coli Protein biosynthesis Biophysics P-site RNA Messenger T arm Ribosomes Molecular Biology |
| Zdroj: | Nature Structural & Molecular Biology. 14:318-324 |
| ISSN: | 1545-9985 1545-9993 |
| DOI: | 10.1038/nsmb1221 |
| Popis: | During the translocation step of protein synthesis, a complex of two transfer RNAs bound to messenger RNA (tRNA-mRNA) moves through the ribosome. The reaction is promoted by an elongation factor, called EF-G in bacteria, which, powered by GTP hydrolysis, induces an open, unlocked conformation of the ribosome that allows for spontaneous tRNA-mRNA movement. Here we show that, in the absence of EF-G, there is spontaneous backward movement, or retrotranslocation, of two tRNAs bound to mRNA. Retrotranslocation is driven by the gain in affinity when a cognate E-site tRNA moves into the P site, which compensates the affinity loss accompanying the movement of peptidyl-tRNA from the P to the A site. These results lend support to the diffusion model of tRNA movement during translocation. In the cell, tRNA movement is biased in the forward direction by EF-G, which acts as a Brownian ratchet and prevents backward movement. |
| Databáze: | OpenAIRE |
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