Translation Flashcards
What are the steps of translation?
1) Initiation
2) Elongation
3) Termination
What are the steps for Prokaryotic initiation?
1) IF3 bind to E site small SU ribosome
2) Small SU ribosome bind shine dalgarno sequence (complementary 16s rRNA)
3) IF1 + GTP at A site (recruits methylated tRNA)
4) IF2 hydrolyse GTP -> GDP+P
5) Large SU binds (30s+70s)
What are the steps for Eukaryotic Initiation?
1) IF1, IF3, IA, IF5 bind small SU ribosome
2) IF2+GTP -> 43s complex
3) tRNA bind p site
4) IF4F complex (A,E,G) binds
5) 43s complex + 5’ cap -> 48s
6) Scan start codon AUG
7) GTP hydrolysis release IFs
8) Large SU binds (60s + 40s)
Compare and contrast the process of translation initiation in prokaryotes and eukaryotes.
- Both bind small ribosome SU to mRNA
- Both recruit tRNA to start codon
- Prokaryotes bind small SU to shine delgarno sequence (16s rRNA) but eukaryotic bind to methylated 5’ cap
- Eukaryotes IF4F recognises 5’ cap to recruits small SU, initiator tRNA+methionine binds start codon
What are the differences between prokaryotes and eukaryotes in translation?
Prokaryotes
- Polycistronic (code multiple protein)
- Shine delgarno sequence 16s rRNA
- EFTUGDP released
- Catalysed by 23s rRNA
Eukaryotes
- Monoistronic (code single)
- Methylated 5’ cap (scan for start codon)
- 3’ Poly A tail (cycling of ribosome)
- Kozak sequence
- EF1aGTP hydrolysed
- Ef2GTP hydrolysed
- Catalysed by 28s rRNA
What are the 3 steps of elongation?
1) Loading
2) Peptidyl transferase reaction
3) Translocation
Discuss importance of RNA and protein during translation elongation
- Ribosome moves along mRNA reading codons adding AA
- Ribosome composed of RNA
- tRNA carries AA to add to peptide chain and recognises codon by base pair interactions
- tRNA has RNA anticodon and protein is site for AA binding
- rRNA catalyses peptide bond form between AA
- Peptidyl transferase reaction carried out by rRNA and positions AA
What are the termination codons?
- UAG
- UGA
- UAA
