Translation

Question 1

How many high energy bonds are used to create each peptide bond in translation?

Answer 1

Four. Two for attachment of an AA by the aminoacyl tRNA synthetases, and two for elongation.

Question 2

What information does the mRNA hold in the translation process?

Answer 2

It is the code! Three letter codons of mRNA decided which AA goes where!

Question 3

So if mRNA is the code, who reads it?

Answer 3

tRNA baby! They deliver the correct AA for each codon by base pairing with their anticodon region.

Question 4

How can tRNAs often recognize multiple codons?

Answer 4

The wobble-pairing at the third location in the codon.

Question 5

So how does tRNA get the right AA on its back?

Answer 5

Aminoacyl tRNA synthetases.

Question 6

So what does that ribosome thing do?

Answer 6

This is the platform… Like platform 9 ¾ from HP.

Question 7

What does the ribosome look like?

Answer 7

It has three tRNA binding sites, A, P, and E… so APE.

Question 8

Which subunit of the ribosome has the catalytic center?

Answer 8

The large subunit… its a BIG catalytic center; the Peptidyl transferase center, PTC.

Question 9

What are the two subunits of the ribosome in Eukaryotes?

Answer 9

40S and 60S subunits.

Question 10

What are the two subunits of the ribosome in Prokaryotes?

Answer 10

30S and 50 S

Question 11

What are the proteins called that help bring the ribosome to the message and assist in assembly of the machinery.

Answer 11

Initiation Factors

Question 12

What proteins deliver tRNAs and move the ribosome down the message?

Answer 12

Elongation Factors (and their partners)

Question 13

What proteins dissociate the subunits from the mRNA at the stop codon?

Answer 13

Termination/recycling factors

Question 14

What site is the start codon (AUG) put in order to start Translation?

Answer 14

P-site

Question 15

In bacteria, what sequence allows the ribosome to bind and where does binding occur?

Answer 15

Shine-Dalgarno sequence; right at the site of the start codon.

Question 16

In Eukaryotes, where does binding of the ribosome occur, and what factor helps that occur?

Answer 16

EIF4E helps bind the ribosome to the 7-methyl guanosine cap of the 5’ end of the mRNA

Question 17

What is the role of an IRES (Internal Ribosome Entry Site)?

Answer 17

IRESs are cap-independent processes to initiate translation.

Question 18

Explain the A-P-E movement of tRNA in Translation.

Answer 18

The A site is the first site of binding, “reading” the message. The peptide bond is formed and the protein is moved from the P site to the A site. Translocation occurs moving the tRNA in the A site to the P site, it then translocates to the E site and eventually out of the ribosome.

Question 19

A codon is changed to encode a different AA – what type of mutation am I?

Answer 19

Missense.

Question 20

A codon is changed but the Same AA is encoded – what type of mutation am I?

Answer 20

Silent.

Question 21

A codon is changed that shifts the reading frame (Addition/Deletion) – what type of mutation am I?

Answer 21

Frame-shift mutation.

Question 22

A codon is changed making a premature stop codon – what type of mutation am I?

Answer 22

Nonsense mutation.

Question 23

A codon is changed removing a stop codon – what type of mutation am I?

Answer 23

Sense Mutation.

Question 24

How could a change in codon change the speed of production?

Answer 24

With varying levels of tRNA with varying binding affinities, it may be hard to find a tRNA with a specific codon, and could slow the speed of production.

Question 25

How could the speed of initiation be regulated?

Answer 25

There could be occlusion of shine-delgarno (bacteria) or factors that inhibit scanning (eukaryotes).

Question 26

How can different AUGs have different “strengths?”

Answer 26

Kozac Context;

Question 27

How can translation be affected at the 5’ cap?

Answer 27

eIF4E can be bound by 4E Binding Proteins that block its function. Phosphorylation blocks their binding, allowing translation initiation.

Question 28

What drug causes dephosphorylation of 4E-BPs and binding to eIF4E to stop translation?

Answer 28

Rapamycin

Question 29

How is translation regulated by eIF2-Alpha?

Answer 29

When eIF2-alpha is phosphorylated, its activity is inhibited and it blocks initiation by blocking the initiator tRNA binding to the ribosome. This can be done by interferon in the cell (as a response to virus).

Question 30

What types of regulation come from 3’ / 5’ UTRs?

Answer 30

All kinds? Binding interactions there do everything from mRNA stability to ribosome binding.

Question 31

What two drugs target inhibiting the peptidyl transferase at the 60S subunit?

Answer 31

Cycloheximide, Anisomycin

Question 32

What are the four drugs inhibiting peptidyl transferase at the 50S subunit?

Answer 32

Erythromycin, Linocomycin, Clindamycin, Chloramphenicol.

Question 33

What drug inhibits tRNA binding at the A-site in prokaryotes?

Answer 33

Tetracycline aminoacyl

Question 34

What drug inhibits initiation and elongation at the 30S subunit?

Answer 34

Streptomycin

Question 35

What drug inhibits initiator tRNA binding at the 30S subunit?

Answer 35

Kasugamycin

Question 36

What drug inhibits phosphorylation of the 4E-BP at MTOR?

Answer 36

Rapamycin