文档介绍：Translation II
1
Translation initiation - big picture
In the absence of mRNA, ribosomes are dissociated
Translation is initiated by recruitment of f-Met-tRNAMet and mRNA to the small ribosomal subunit
Recruitment is facilitated by a number of initiation factors
Initiation plex in eukaryotes but simpler in prokaryotes
There are many more levels of control in eukaryotes
2
Initiation prokaryotes vs. eukaryotes
prokaryotes
eukaryotes
From: Hershey & Merrick in “Translational Control of Gene expression” pp. 33-88”, Sonenberg, Hershey, Matthews, eds. CSH Press 2000
3
Translation initiation in prokaryotes
There are few Initiation factors
IF1 ( kDa)
binds after ribosome dissociation,
binds to A-site of small subunit
assists IF2 and IF3
IF2 ( kDa), homologous to eIF5B
binds fMet-tRNAi
GTPase
IF3 ( kDa)
ribosome anti-association
Involved in tRNAi-codon interaction, decoding
Assures together with IF2 that fMet-tRNAini is bound not any other
W2 (71 kDa), ATPase, eIF4A (helicase) homolog?
Little known, no solid evidence for helicase function, stimulates in-vitro translation of some mRNA with secondary structure around AUG
EF-P (21 kDa), eIF5A homolog
Little known
4
Model for Initiation in Prokaryotes
Dissociation of ribosome due to absence of mRNA and aided by IF3 binding to 30S
IF3 was the earliest- and most-studied bacterial initiation factor
Association to