June 26, 2005
Textbook Explanation of mRNA Translation May Need Rethinking
Our understanding of how messenger RNAs are translated into proteins is challenged by new research published today in the Open Access journal Journal of Biology. The study suggests that EF-G, the GTPase that facilitates tRNA translocation in bacteria, enters the ribosome bound to a different guanine nucleotide than previously thought "“ GDP, not GTP. The ribosome itself then seems to act as the guanine-nucleotide exchange factor, not some as-yet-unidentified factor as previously assumed. This finding questions the prevailing model for RNA translocation.
According to the textbook model EF-G provides the energy needed for the translocation phase of translation by bringing GTP into the ribosome where GTP is subsequently hydrolysed into GDP.
These findings differ radically from all previous models and as such may represent a considerable step forward in our understanding of translocation, a fundamental mechanism in protein synthesis and gene expression. RNA translation is a highly conserved mechanism and these results using a bacterial system are likely to be applicable to higher organisms as well. This should spur more research in the field to confirm or disprove the findings and give us a clearer picture of RNA translation. In particular, the present clarification of the translocation process at the biochemical level may allow a deeper understanding of how relative movements of the ribosomal subunits can accomplish thousands of translocation events without frame-shifting or loss of tRNA-bound nascent protein chains during peptide elongation.
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