Protein Synthesis Flashcards
Where is the cap found on mRNA and what is its purpose?
Found on 5’ end and it protects from nuclease digestion and it is also a binding site for eIF4E.
Where is the poly A tail found and what is its role?
Found on 3’ end and it protects from enzymatic degradation, aids in transcription termination.
What is tRNA?
Single stranded RNA which forms stems and loops.
What is the important loop and stem formed by tRNA?
Anticodon loop and the acceptor stem where the amino acids link.
What type of activity does the 80S ribosome have?
Peptidyl transferase activity which is associated with the 60S subunit and allows the formation of peptide bonds.
What are the 3 stages of translation?
Initiation, elongation and termination.
Why is initiation the rate limiting step?
It depends on the population of eukaryotic initiation factors in cytoplasm.
What are the 3 main steps in initiation?
- Assembly of 43S pre-initiation complex
- Binding of mRNA to 43S complex
- Assembly of 80S initiation complex
Which eukaryotic initiation factor has a high affinity for met-tRNA?
eIF2 which associates with met-tRNA and GTP and forms ternary complex.
What eukaryotic initiation factor recognised 40S ribosome?
eIF3 which binds to it and forms 43S subunit.
What forms the 43S pre initiation complex?
43S and the ternary complex.
Which eukaryotic initiation factor binds to CAP on mRNA?
eIF4E as it recognises the 5’ end CAP.
What are the next steps after eIF4E binds?
eIF4G binds to eIF4E and eIF4A unwinds mRNA secondary structures as it has helicase activity.
How is the 48S pre initiation complex formed?
43S complex binds to eIF4G via eIF3.
What is scanning?
Ribosomal scanning is the movement of the ribosome along the mRNA to find the start codon AUG.
