Protein synthesis pt. 2 Flashcards
What are the prokaryotic initiation factors (protein synth)?
IF1
IF2
IF3
What are the prokaryotic elongation factors (protein synth)?
EF-Tu
EF-Ts
EF-G
What are the prokaryotic release factors?
RF1
RF2
RF3
Which initiation, elongation, and release factors require GTP for energy?
IF2-GTP
EF-Tu-GTP
EF-G-GTP
RF3-GTP
Eukaryotes:
EiF2-GTP
Which enzyme attaches ATP to amino acids prior to tRNA loading?
Aminoacyl tRNA synthetase
Which enzyme attaches the activated amino acid to tRNA?
Aminoacyl-tRNA:synthetase
What is the ratio of aminoacyl-tRNA synthetase to amino acids?
One enzyme for EACH amino acid. But that enzyme performs both steps of loading/activating.
The 2 step process of AA activation and tRNA loading requires the cleavage of _____ high energy bonds.
2
Which step of tRNA loading is the key step in controlling the accuracy of synthesis?
AA activation because the synthetase must recognize a specific AA R group AND the corresponding tRNA
How does Aminoacyl tRNA synthetase correct errors?
Hydrolytic site on the enzyme. Important because there are no other chances for correction after the synthetase leaves!
What is the start codon? Is it the same in prok and euk?
AUG (methionine)
Prokaryote is a modified methionine (fmet)
How is the start codon located?
Shine Dalgarno sequence
What is the main initiation factor?
IF2-GTP
What is the Shine-Dalgarno sequence?
A purine rich sequence 7-10 bps upstream of the AUG start codon
It is complementary to the 16s RNA
In _______, ________ adds a formyl group to the initiator tRNA methionine.
Prokaryotes, transformylase
What are the 3 pockets of the ribosome?
A, P, E sites
aminoacyl, peptidyl, exit
What are the 3 stop codons?
UAA, UAG, UGA
Because it is much more efficient, multiple ribosomes will translate one mRNA simultaneously. This product is called a ________.
Polyribosome
How does tetracycline work?
Binds to the A site of prokaryotic ribosomes.to block binding of aminoacyl-tRNA to A site.
How does chloramphenicol work?
Resembles a peptide bond; competitively inhibits peptidyl transferase activity in prokaryotes. Inhibits the activity at the 23s rna.
The initiator tRNA associates with which site/pocket on the ribosome?
P site
What is the eukaroytic equivalent of the shine delgarno sequence?
Kozak sequence
What is the primary initiation factor in eukaryotes?
eIF2-GTP
Where does the small subunit bind in prokaryotes? in Eukaryotes?
At AUG codon in prokaryotes, at cap in eukaryotes
What is the role of eIF4G in eukaroytic initiation?
Scaffold protein
What is the role of eIF4E in eukaryotic initiation?
Facilitates binding of small subunit eIF3-initiator tRNA-eIF2-GTP
Which subunits unwind secondary structure for eukaryotic translation?
eIF4A and eIF4B
What does the small subunit-eIF3 initiator and tRNA-eiF2-GTP do?
scan the mRNA to find the AUG initiation codon (in Kozak sequence)
What is the last step of eukaryotic translation?
eIF5 causes release of factors and GTP is hydrolyzed to join large subunit.
Where do the initiation subunits bind in prokaryotes versus eukaryotes?
In prokaryote, it binds the AUG in the shine delgarno sequence. In eukaryotes, it binds the 5’ cap and then scans down to find the kozak sequence
