TAILIEUCHUNG - Báo cáo sinh học: "Guanine-nucleotide exchange on ribosome-bound elongation factor G initiates the translocation of tRNAs"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Guanine-nucleotide exchange on ribosome-bound elongation factor G initiates the translocation of tRNAs. | J. Biol. Journal of Biology BioMed Central Research article Open Access Guanine-nucleotide exchange on ribosome-bound elongation factor G initiates the translocation of tRNAs Andrey V Zavialov Vasili V Hauryliuk and Mâns Ehrenberg Address Department of Cell and Molecular Biology Biomedical Center Uppsala University SE-75124 Uppsala Sweden. Correspondence Mâns Ehrenberg. E-mail ehrenberg@ Received 17 January 2005 Revised 23 March 2005 Accepted 19 April 2005 Published 27 June 2005 Journal of Biology 2005 4 9 The electronic version of this article is the complete one and can be found online at http content 4 2 9 2005 Zavialov et al. licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License http licenses by which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. Abstract Background During the translation of mRNA into polypeptide elongation factor G EF-G catalyzes the translocation of peptidyl-tRNA from the A site to the P site of the ribosome. According to the classical model EF-G in the GTP-bound form promotes translocation while hydrolysis of the bound GTP promotes dissociation of the factor from the post-translocation ribosome. According to a more recent model EF-G operates like a motor protein and drives translocation of the peptidyl-tRNA after GTP hydrolysis. In both the classical and motor protein models GDP-to-GTP exchange is assumed to occur spontaneously on free EF-G even in the absence of a guanine-nucleotide exchange factor GEF . Results We have made a number of findings that challenge both models. First free EF-G in the cell is likely to be in the GDP-bound form. Second the ribosome acts as the GEF for EF-G. Third after guanine-nucleotide exchange EF-G in the GTP-bound form moves the tRNA2-mRNA complex to an intermediate translocation state in which the mRNA is partially .

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