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The translation of genetic information into proteins is a fundamental process of life. Stepwise addition of amino acids to the growing polypeptide chain requires the coordinated movement of mRNA and tRNAs through the ribosome, a process known as translocation. Here, we review current understanding of the kinetics and mechanics of translocation, with particular emphasis on the structure of a functional mammalian ribosome stalled during translocation by an mRNA pseudoknot. In the context of a pseudoknot-stalled complex, the translocase EF-2 is seen to compress a hybrid-state tRNA into a strained conformation. We propose that this strain energy helps overcome the kinetic barrier to translocation and drives tRNA into the P-site, with EF-2 biasing this relaxation in one direction. The tRNA can thus be considered a molecular spring and EF-2 a Brownian ratchet in a "spring-and-ratchet" system within the translocation process.

Original publication

DOI

10.1016/j.str.2008.04.001

Type

Journal article

Journal

Structure

Publication Date

05/2008

Volume

16

Pages

664 - 672

Keywords

Animals, Kinetics, Mammals, Models, Molecular, Movement, Nucleic Acid Conformation, Peptide Elongation Factor 2, Protein Biosynthesis, RNA, Messenger, RNA, Transfer, Ribosomes