Offner Protein Synthesis Flashcards

1
Q

Factors required for protein synthesis

A

IF2-GTP
EFTU-GTP
EF-G-GTP
RF-3-GTP

  • add “e” for eukaryotic
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2
Q

How are amino acids attached to tRNAs?

A

Uses synthetase for both steps
- amino acids activated with ATP to aminoacyl adenylate
- tRNA added to form aminoacyl-tRNA + AMP

Requires cleavage of 2 high-energy bonds

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3
Q

Structure of amino acid synthetase

A
  • activation site
  • hydrolytic site (corrects errors)
  • aa-tRNA that leave enzyme cannot be error corrected
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4
Q

Initiation of prokaryotic protein synthesis

A

Initiation complex binds to Shine-delgarno sequence
- initiator tRNA binds in P site

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5
Q

Prokaryotic protein initiation complex

A

Contains tRNA, fMET, IF2-GTP
- 30S and 50S bind, causing release of IF1, IF3, IF2-GDP

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6
Q

Which subunit and part binds with the Shine-Dalgarno sequence

A

It base pairs with 3’ end of 16S rRNA of the 30S subunit

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7
Q

How is fMET created?

A

Formyl group added to initiator tRNA after activation with Methionine

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8
Q

Translation elongation mechanism

A
  • EF-Tu-GTP puts tRNA in A site
  • Peptidyl transferase creates peptide bond
  • EF-G-GTP cases translocation of ribosome
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9
Q

Translation Termination mechanism

A
  • RF1/2 bind A site, RF3-GTP binds common site
  • Peptidyl transferase cleaves ester bond via GTP
  • release of everything
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10
Q

How is peptidyl transferase made, and which subunit is a part of?

A

Ribozyme, part of 23S or 28S rRNA

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11
Q

How does EF-G-GTP cause translocation of the ribosome

A

Hydrolysis of GTP

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12
Q

What is the common site on the prokaryotic ribosome

A

Where TF, EF and RF all bind
- ensures stepwise progression of synthesis (not all at same time)

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13
Q

What do polyribosomes do

A

Make multiple proteins from the same message
- simultaneous message transcription

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14
Q

What do Tetracycline, Chloramphenicol and Puromycin do, and do they affect prokaryotes or eukaryotes?

A

Inhibit translation, all affect prokaryotes, only puromycin affects eukaryotes

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15
Q

Tetracyline

A

Prokaryotes only
- blocks binding of aminoacyl-tRNA to A site

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16
Q

Chloroamphenicol

A

Prokaryotes only
- resembles peptide bond
- inhibits peptidy transferase

17
Q

Puromycin

A

Prok and Euk
- enters A site
- accepts polypeptide chain
- blocks translocation

18
Q

How many ATP/GTP hydrolyzed per 100 amino acids for:
Activation, Initiation, Elongation EF-Tu and EF-G, Termination

A

Activation: 200ATP
Initiation: 1GTP
Elongation EF-TU: 99 GTP
Elongation EF-G: 99GTP
Termination RF-3: 1GTP

400 total

19
Q

Eukaryotic translation initiation

A
  • small subunit binds at cap
  • 40S scans from cap to find Kozak sequence (CCACCAUGG)
  • GTP used to join 60S to 40S
20
Q

Cap binding proteins

A

eIF4G - scaffold
eIF4A- Helicase
eIF4B - ATPase
eIF4E - binds eIF3 on 40S

21
Q

Role of eIF4B and eIF4A

A

Combine to unwind secondary structure

22
Q

Role of eIF4E

A

Facilitates binding of 40S and initiator tRNA-eIF2-GTP complex

23
Q

Role of eIF5

A

Releases 40S associated factors, combines it with 60S using GTP to begin translation

24
Q

How are ribosomes recycled in eukaryotes

A

mRNA loop structure

25
Q

HCV lifecycle

A

1) tRNA into cell
2) creation of viral proteins
3) negative RNA produced, replicated to create positive RNA for export

26
Q

HCV 5A and 5B proteins

A

5A: replication complex protein
5B: RNA-dependent RNA Pol

27
Q

How is HCV treated

A

Target 5A and 5B

28
Q

Is HCV RNA capped?

A

No, but it contains IRES: structural feature which allows ribosome to bind for replication

29
Q

Does the Shine-Dalgarno sequence contain mainly pyrimidines or purines

A

‘tis purine-rich