Flashcards in 2017 Biochemistry - Protein Synthesis Deck (16):
Importance of the 3' end of tRNA?
Amino Acid binding site
Importance of the TYC loop of tRNA?
Where tRNA binds to Ribosome
Importance of the D loop of tRNA?
Contains high amounts of dihydrouridine residues (this is recognized by the enzyme tRNA synthetase)
Importance of the ANTICODON loop of tRNA?
Contains the Anticodon which is complementary to the codon of the messenger RNA
How does tRNA and mRNA bind? Parallel or Antiparallel?
tRNA runs: 3'-5'
mRNA read: 5'-3'
How does initiation w/ tRNA and the Ribosome work?
1. Initiation factors dissociate the 70S (80S in eukaryotes) into the parts of 50S & 30S (40S & 60S)
2. tRNA-Met and mRNA bind the 40S subunit with the help of eIF2. tRNA-fMet (formyl methionine) is the initiation codon for prokaryotes.
3. The big subunit (60S or 50S) reassemble with the smaller unit and the tRNA-Met introduces the first AA (methionine) into a protein. It binds to the initiation Codon (AUG).
What are the 4 Initiation factors for eukaryotes and what do they do?
eIF-1A & eIF-3: bind 40S
eIF-4F: mRNA complex binds to ribosome subunit
eIF-2: (GTP) binds to tRNA-met which binds AUG
eIF-2: lost as GTP is hydrolyzed and 80S unit formed
Function of A, P, E sites of Ribosome?
A - Acceptor: accepts incoming tRNA
P - Peptide: site where peptide bond is formed for new tRNA as protein is being constructed.
E - Exit
What is required for new peptide bond formation?
Elongation Factor 1A (eEF1A) and 1-GTP
What is required for Translocation?
This is the movement of the ribosome one-codon down the mRNA.
-eEF2 & GTP
What is required for Termination?
Stop codon is reached at the A-site
Releasing factors: eRF1 and eRF3
What are the energy requirements for A.A. tRNA activation and for Elongation/Termination?
4 Total high energy bonds
What is the importance of signal peptides?
Only in Eukaryotic cells, helps direct Ribosomes to go from cytoplasm to ER, shuttling the protein into the ER for further processing.
Signal Recognition Particle (SRP) - binds to peptide as it is expelled from Ribosome and prevents translation until ribosome docks with ER.
GTP dependent process - Ribosome binding
ATP depended - transport protein through the Ribosome membrane.
Name 2 Eukaryotic Protein Synthesis Inhibitors and what they inhibit (specifically)?
Cycloheximide - inhibit peptide bond formation
Diphtheria toxin - catalyze reaction of NAD+ w/ elongation factor, results in inhibition of translocation
Name 2 Eukaryotic & Prokaryotic Protein Synthesis Inhibitors and what they inhibit (specifically)?
Chloramphenicol - inhibit peptide bond formation & mitochondrial protein synthesis at high levels
Puromycin - causes premature termination