Initiation of eukaryotic translation Flashcards
Is translation initiation much simpler in bacteria or in eukaryotic cytosol?
In bacteria
Do cap-binding and tail-binding proteins recognise each other?
Yes, so eukaryotic mRNA is a ‘non-closed’ loop during translation
What are the initiation codons?
AUG»_space; GUG
What is the special initiator tRNA?
tRNAi
Does eukaryotic translation involve transformylase?
No
How is eukaryotic translational initiation different from prokaryotic translational initiation?
- No Shine-Dalgarno (S-D) recognition (RNA-RNA)
- 40S binds to mRNA-CAP (protein-protein)
- Complexity_multiplicity of eIFs
What are the functions of eIFs?
- Bind to ribosomal subunits: eIF1, eIF1A, eIF3, eIF5, eIF6
- Bind to met-tRNAi: eIF2
- Bind to mRNA CAP: eIF4 group
- Release other eIFs: eIF5, eIF5B
What are the functions of eIFs?
- Bind to ribosomal subunits: eIF1, eIF1A, eIF3, eIF5, eIF6
- Bind to met-tRNAi: eIF2
- Bind to mRNA CAP: eIF4 group
- Release other eIFs: eIF5, eIF5B
How many factors does eIF1 contain?
2 (1+1A)
How many subunits does eIF2 contain?
3
How many subunits does eIF2B contain?
5
How many subunits does eIF3 contain?
13-8
How many factors does eIF4 contain?
4 (4A, 4B, 4E, 4G)
How many factors does eIF5 contain?
2 (5+5B)
How many polypeptide does eIF6 contain?
A single polypeptide
Various eIFs can bind to free ribosomal subunits and prevent the from doing what?
Prevent them from forming 80S ribosomes
What ribosomal subunits are needed for translational initiation?
Free 40S and 60S subunits
What does 43S PIC do?
‘Scans’ along mRNA towards START codon
Initiation usually begins at the first AUG encountered by the scanning complex, however if the context is not optimal then what can happen to the scanning?
The scanning sometimes continues to next AUG
