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A new tRNA intermediate revealed on the ribosome during EF4-mediated back-translocation

Connell, S.R. and Topf, Maya and Qin, Y. and Wilson, D.N. and Mielke, T. and Fucini, P. and Nierhaus, K.H. and Spahn, C.M.T. (2008) A new tRNA intermediate revealed on the ribosome during EF4-mediated back-translocation. Nature Structural & Molecular Biology 15 , pp. 910-915. ISSN 1545-9985.

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EF4 (LepA) is an almost universally conserved translational GTPase in eubacteria. It seems to be essential under environmental stress conditions and has previously been shown to back-translocate the tRNAs on the ribosome, thereby reverting the canonical translocation reaction. In the current work, EF4 was directly visualized in the process of back-translocating tRNAs by single-particle cryo-EM. Using flexible fitting methods, we built a model of ribosome-bound EF4 based on the cryo-EM map and a recently published unbound EF4 X-ray structure. The cryo-EM map establishes EF4 as a noncanonical elongation factor that interacts not only with the elongating ribosome, but also with the back-translocated tRNA in the A-site region, which is present in a previously unseen, intermediate state and deviates markedly from the position of a canonical A-tRNA. Our results, therefore, provide insight into the underlying structural principles governing back-translocation.

Item Type: Article
School or Research Centre: Birkbeck Schools and Research Centres > School of Science > Biological Sciences
Depositing User: Administrator
Date Deposited: 04 Aug 2010 14:09
Last Modified: 11 Oct 2016 12:01

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