Translation - DNA to RNA to protein Flashcards
1
Q
Initiation of translation in prokaryotic - Shine-Dalgarno / Ribosome Binding Site
A
- A sequence upstream from the mRNA’s start codon that tells the ribosome where to start translating
- Binds the 16S rRNA
2
Q
Components required for prokaryotic translation
A
- Ribosomes
- mRNA
- fMet-tRNA(fmet)
- initiation factors (IFs)
3
Q
What is needed for the assembly of the translation apparatus?
A
One molecule of GTP
4
Q
How translation is intiated in prokaryotes
A
- Initiating tRNA (fMet-tRNA(fMet)), small ribosomal subunit + mRNA form a complex
- This is followed by binding of large ribosomal subunit
- Then ready for elongation phase
5
Q
Initiation of translation in eukaryotic - eIF
A
- ‘Eukaryotic Initiation Factors’ help the ribosome bind to the 5’-Cap and find the first AUG codon (start)
- Don’t contain a Shine-Dalgarno sequence or equivalent
6
Q
How translation is initiated in eukaryotes
A
- Initiating tRNA (Met-tRNA(Met), small ribosomal subunit and the mRNA form a complex
- Then large ribosomal subunit binds
- Ready for elongation phase
7
Q
Components required for eukaryotes
A
- Ribosome
-mRNA - Initiation Factors (eIFs)
8
Q
What is needed for the assembly of translation apparatus in eukaryotes?
A
1 ATP + 1 GTP
9
Q
The P (peptidyl) Site - Step 1
A
- At beginning of each cycle, the growing peptide chain is attached to the tRNA
10
Q
The A (aminoacyl) Site - Step 2
A
- Incoming aminoacyl-tRNA is delivered by an elongation factor (EF-Tu/eEF1alpha) to here - GTP needed
- A decoding centre in A make sure the right aa-tRNA is delivered
11
Q
How the peptide bond is formed - Step 3
A
- Growing chain is transferred from t-RNA in P site
- To the amino group of the AA is carried by the tRNA in the A site
- Peptide bond is formed
- The peptidyl transfer reaction is catalysed by peptidyltransferase activity of ribosome
12
Q
Ribosome moves along the mRNA - Step 4
A
- This translocation step requires an elongation factor (EG-G/eEF2) and GTP
- tRNA carrying the growing peptide –> P site
- Uncharged tRNA –> Exit site (E)
- A site is now occupied by next codon on mRNA
13
Q
Where the uncharged tRNA goes + how the cycle continues - Step 5
A
- Leaves the ribosome and the next aminoacyl-tRNA is delivered to the A site by EF-Tu
14
Q
Termination of translation
A
- When the stop codon occupies the A site, no aminoacyl-tRNA can bind to A site
- Release factors bind to A site to release new protein from ribosome
- Factors (RRF, EF-G, IF3) lead to release of uncharged tRNAs & large + small ribosomal subunits dissociate
