Heterogeneous pathways and timing of factor departure during translation initiation
A single-molecule approach is used to investigate the kinetics of assembly of the translation initiation complex, revealing that there is more than one pathway by which the necessary factors can assemble. Kinetics of translation initiation Translation initiation involves the association of the two r...
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Veröffentlicht in: | Nature (London) 2012-07, Vol.487 (7407), p.390-393 |
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Zusammenfassung: | A single-molecule approach is used to investigate the kinetics of assembly of the translation initiation complex, revealing that there is more than one pathway by which the necessary factors can assemble.
Kinetics of translation initiation
Translation initiation involves the association of the two ribosomal subcomplexes and a host of initiation factors. Joseph Puglisi and colleagues use a sophisticated single-molecule approach to look at the kinetics of assembly of the translation initiation complex. They find that there is more than one pathway by which the factors can assemble, and identify the crucial event that transitions the complex from initiation to elongation.
The initiation of translation establishes the reading frame for protein synthesis and is a key point of regulation
1
. Initiation involves factor-driven assembly at a start codon of a messenger RNA of an elongation-competent 70S ribosomal particle (in bacteria) from separated 30S and 50S subunits and initiator transfer RNA. Here we establish in
Escherichia coli
, using direct single-molecule tracking, the timing of initiator tRNA, initiation factor 2 (IF2; encoded by
infB
) and 50S subunit joining during initiation. Our results show multiple pathways to initiation, with orders of arrival of tRNA and IF2 dependent on factor concentration and composition. IF2 accelerates 50S subunit joining and stabilizes the assembled 70S complex. Transition to elongation is gated by the departure of IF2 after GTP hydrolysis, allowing efficient arrival of elongator tRNAs to the second codon presented in the aminoacyl-tRNA binding site (A site). These experiments highlight the power of single-molecule approaches to delineate mechanisms in complex multicomponent systems. |
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ISSN: | 0028-0836 1476-4687 |
DOI: | 10.1038/nature11172 |