Protein synthesis pt. 2

Question 1

What are the prokaryotic initiation factors (protein synth)?

Answer 1

IF1
IF2
IF3

Question 2

What are the prokaryotic elongation factors (protein synth)?

Answer 2

EF-Tu
EF-Ts
EF-G

Question 3

What are the prokaryotic release factors?

Answer 3

RF1
RF2
RF3

Question 4

Which initiation, elongation, and release factors require GTP for energy?

Answer 4

IF2-GTP
EF-Tu-GTP
EF-G-GTP
RF3-GTP

Eukaryotes:
EiF2-GTP

Question 5

Which enzyme attaches ATP to amino acids prior to tRNA loading?

Answer 5

Aminoacyl tRNA synthetase

Question 6

Which enzyme attaches the activated amino acid to tRNA?

Answer 6

Aminoacyl-tRNA:synthetase

Question 7

What is the ratio of aminoacyl-tRNA synthetase to amino acids?

Answer 7

One enzyme for EACH amino acid. But that enzyme performs both steps of loading/activating.

Question 8

The 2 step process of AA activation and tRNA loading requires the cleavage of _____ high energy bonds.

Answer 8

2

Question 9

Which step of tRNA loading is the key step in controlling the accuracy of synthesis?

Answer 9

AA activation because the synthetase must recognize a specific AA R group AND the corresponding tRNA

Question 10

How does Aminoacyl tRNA synthetase correct errors?

Answer 10

Hydrolytic site on the enzyme. Important because there are no other chances for correction after the synthetase leaves!

Question 11

What is the start codon? Is it the same in prok and euk?

Answer 11

AUG (methionine)

Prokaryote is a modified methionine (fmet)

Question 12

How is the start codon located?

Answer 12

Shine Dalgarno sequence

Question 13

What is the main initiation factor?

Answer 13

IF2-GTP

Question 14

What is the Shine-Dalgarno sequence?

Answer 14

A purine rich sequence 7-10 bps upstream of the AUG start codon

It is complementary to the 16s RNA

Question 15

In _______, ________ adds a formyl group to the initiator tRNA methionine.

Answer 15

Prokaryotes, transformylase

Question 16

What are the 3 pockets of the ribosome?

Answer 16

A, P, E sites

aminoacyl, peptidyl, exit

Question 17

What are the 3 stop codons?

Answer 17

UAA, UAG, UGA

Question 18

Because it is much more efficient, multiple ribosomes will translate one mRNA simultaneously. This product is called a ________.

Answer 18

Polyribosome

Question 19

How does tetracycline work?

Answer 19

Binds to the A site of prokaryotic ribosomes.to block binding of aminoacyl-tRNA to A site.

Question 20

How does chloramphenicol work?

Answer 20

Resembles a peptide bond; competitively inhibits peptidyl transferase activity in prokaryotes. Inhibits the activity at the 23s rna.

Question 21

The initiator tRNA associates with which site/pocket on the ribosome?

Answer 21

P site

Question 22

What is the eukaroytic equivalent of the shine delgarno sequence?

Answer 22

Kozak sequence

Question 23

What is the primary initiation factor in eukaryotes?

Answer 23

eIF2-GTP

Question 24

Where does the small subunit bind in prokaryotes? in Eukaryotes?

Answer 24

At AUG codon in prokaryotes, at cap in eukaryotes

Question 25

What is the role of eIF4G in eukaroytic initiation?

Answer 25

Scaffold protein

Question 26

What is the role of eIF4E in eukaryotic initiation?

Answer 26

Facilitates binding of small subunit eIF3-initiator tRNA-eIF2-GTP

Question 27

Which subunits unwind secondary structure for eukaryotic translation?

Answer 27

eIF4A and eIF4B

Question 28

What does the small subunit-eIF3 initiator and tRNA-eiF2-GTP do?

Answer 28

scan the mRNA to find the AUG initiation codon (in Kozak sequence)

Question 29

What is the last step of eukaryotic translation?

Answer 29

eIF5 causes release of factors and GTP is hydrolyzed to join large subunit.

Question 30

Where do the initiation subunits bind in prokaryotes versus eukaryotes?

Answer 30

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