4. Translation Flashcards
Frame shifting
Three different frames to read a codon sequence
Which end is amino acid attached to
3’ end
Loading amino acid on tRNA
- Amino acid is adenylated with ATP (Amino Acid - PO4 - Adenine)
- Amino acid is added onto tRNA and AMP is released
Bond type in aminoacyl tRNA
Ester bond
Editing tRNA
Synthesis site and Editing site - like P and E in Polymerase
Protein synthesis direction (Protein)
N terminus to C terminus
Protein synthesis direction (RNA)
5’ to 3’
Ribosome size
70s - Prokaryote
80s - Eukaryote
Sites in Ribosome
A - Aminoacyl
P - Peptidyl
E - Exit
Initiation of Translation
- Small subunit binds Methionine at P site with elF2 and GTP.
- Small subunit recognizes poly-A-tail/5’cap complex
- Small subunit binds to 5’ end and moves downstream till it finds the first AUG it finds - Uses ATP to move down
- When it reaches AUG, the large subunit binds to the small subunit
- GTP is hydrolyzed to remove all the other factors
Elongation of Translation
- The peptide ester bond between the tRNA and AA at P site is broken and the protein chain is transferred to the tRNA on the A site forming a peptide bond.
- This release of energy moves the large subunit a codon downstream
- The P site tRNA leaves through the E site and the small subunit follows the large subunit
Proofreading of ribosome
- tRNAs are bound to EF-tu that carries GTP
- The GTP is hydrolyzed, pushing the tRNA onto the A site and swinging around.
- If the hydrogen bond is strong enough, the tRNA will stick and the protein will be made
Termination of Translation
- Release factor binds to A site
- The ester bond is hydrolyzed and the protein is released
- Everything falls apart
EF-tu
Elongation Factor thermo unstable
- Proofreading of tRNA
hsp 70
Uses ATP to destabilize the protein
hsp 60
A “container” that places protein inside to help re-fold it
Uses ATP to put cap on and off
Proteasome
Unfoldase ring on each side with protease in the middle
Digestion of protein
- Unfoldase ring recognizes the polyubiquitin chain
2. The protein is pushed into the protease
Pulling of Protein into protease
The “cap” has six subunits - like helicase
- E from hydrolysis of ATP is used to change the conformation and pull it in
Activation of Ubiquitin Ligase
- Phosphorylation by protein kinase
- Allosteric transition by ligand binding
- Allosteric Transition by protein binding
Activation of Degradation Signal
- Phosphorylation by protein kinase
- Unmasking by protein dissociation
- Creation of destabilizing N-terminus (Through hydrolysis)
