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Anuradha Seshadri 《Journal of molecular biology》2010,401(5):854-865
In eubacteria, ribosome recycling factor (RRF) and elongation factor G (EFG) function together to dissociate posttermination ribosomal complexes. Earlier studies, using heterologous factors from Mycobacterium tuberculosis in Escherichia coli revealed that specific interactions between RRF and EFG are crucial for their function in ribosome recycling. Here, we used translation factors from E. coli, Mycobacterium smegmatis and M. tuberculosis, and polysomes from E. coli and M. smegmatis, and employed in vivo and in vitro experiments to further understand the role of EFG in ribosome recycling. We show that E. coli EFG (EcoEFG) recycles E. coli ribosomes with E. coli RRF (EcoRRF), but not with mycobacterial RRFs. Also, EcoEFG fails to recycle M. smegmatis ribosomes with either EcoRRF or mycobacterial RRFs. On the other hand, mycobacterial EFGs recycle both E. coli and M. smegmatis ribosomes with either of the RRFs. These observations suggest that EFG establishes distinct interactions with RRF and the ribosome to carry out ribosome recycling. Furthermore, the EFG chimeras generated by swapping domains between mycobacterial EFGs and EcoEFG suggest that while the residues needed to specify the EFG interaction with RRF are located in domains IV and V, those required to specify its interaction with the ribosome are located throughout the molecule. 相似文献
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Ribosome recycling is a process which dissociates the post-termination complexes (post-TC) consisting of mRNA-bound ribosomes
harbouring deacylated tRNA(s). Ribosome recycling factor (RRF), and elongation factor G (EFG) participate in this crucial
process to free the ribosomal subunits for a new round of translation. We discuss the overall pathway of ribosome recycling
in eubacteria with especial reference to the important role of the initiation factor 3 (IF3) in this process. Depending on
the step(s) at which IF3 function is implicated, three models have been proposed. In model 1, RRF and EFG dissociate the post-TCs
into the 50S and 30S subunits, mRNAand tRNA(s). In this model, IF3, which binds to the 30S subunit, merely keeps the dissociated
subunits apart by its anti-association activity. In model 2, RRF and EFG separate the 50S subunit from the post-TC. IF3 then
dissociates the remaining complex of mRNA, tRNA and the 30S subunit, and keeps the ribosomal subunits apart from each other.
However, in model 3, both the genetic and biochemical evidence support a more active role for IF3 even at the step of dissociation
of the post-TC by RRF and EFG into the 50S and 30S subunits. 相似文献
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