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Mechanism and Rates of Exchange of L7/L12 between Ribosomes and the Effects of Binding EF-G
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2012 (English)In: ACS Chemical Biology, ISSN 1554-8929, Vol. 7, no 6, 1120-1127 p.Article in journal (Refereed) Published
Abstract [en]

The ribosomal stalk complex binds and recruits translation factors to the ribosome during protein biosynthesis. In Escherichia coli the stalk is composed of protein L10 and four copies of L7/L12. Despite the crucial role of the stalk, mechanistic details of L7/L12 subunit exchange are not established. By incubating isotopically labeled intact ribosomes with their unlabeled counterparts we monitored the exchange of the labile stalk proteins by recording mass spectra as a function of time. On the basis of kinetic analysis, we proposed a mechanism whereby exchange proceeds via L7/L12 monomers and dimers. We also compared exchange of L7/L12 from free ribosomes with exchange from ribosomes in complex with elongation factor G (EF-G), trapped in the posttranslocational state by fusidic acid. Results showed that binding of EF-G reduces the L7/L12 exchange reaction of monomers by similar to 27% and of dimers by similar to 47% compared with exchange from free ribosomes. This is consistent with a model in which binding of EF-G does not modify interactions between the L7/L12 monomers but rather one of the four monomers, and as a result one of the two dimers, become anchored to the ribosome-EF-G complex preventing their free exchange. Overall therefore our results not only provide mechanistic insight into the exchange of L7/L12 monomers and dimers and the effects of EF-G binding but also have implications for modulating stability in response to environmental and functional stimuli within the cell.

Place, publisher, year, edition, pages
2012. Vol. 7, no 6, 1120-1127 p.
National Category
Biological Sciences
URN: urn:nbn:se:uu:diva-178681DOI: 10.1021/cb300081sISI: 000305207400021OAI: oai:DiVA.org:uu-178681DiVA: diva2:542638
Available from: 2012-08-02 Created: 2012-08-01 Last updated: 2012-08-02Bibliographically approved

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Koripella, Ravi KiranSanyal, Suparna
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Structure and Molecular Biology
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