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MHG - Exam I > Lecture 6-Translation (Rosenthal) > Flashcards

Lecture 6-Translation (Rosenthal) Flashcards

1
Q

How many aa’s are there for prokaryotes? Eukaryotes?

A
  • 20

- 20

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2
Q

How many tRNAs are there for prokaryotes? Eukaryotes?

A
  • 20+

- 20+

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3
Q

The aa code is degenerate meaning _____.

A

There are multiple codons for each aa

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4
Q

Explain what happens when each respective nucleotide is in the wobble position of the codon.

A
  • A/C: there is only 1 tRNA that can read it, they cannot pair with anything else
  • G/U: 2 tRNAs can read these: G can bp w/C or U; U can bp with A or G
  • I: 3 different codons can recognize because it can bp with A, U, C
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5
Q

How many tRNAs total are there for the 20aas including the starter Met?

A

32

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6
Q

Activation of tRNAs requires what 4 things?

A
  • tRNAs
  • aminoacyl tRNA synthetase (and therefore ATP)
  • specific aa for tRNA
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7
Q

Which site on the aminoacyl tRNA synthetase is responsible for the proofreading activity?

A

Hydrolytic site

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8
Q

CMT1

A

CMT is one of the most common inherited nerve disorders: mutation in an aminoacyl-tRNA synthetase resulting in polyneuropathies

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9
Q

CMT2. Type 2D?

A

mutation in an aminoacyl-tRNA synthetase resulting in axonal polyneuropathies.
- Type 2D: glycyl-tRNA synthetase gene (GARS)

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10
Q

intermediate CMT. Type C?

A

mutation in an aminoacyl-tRNA synthetase
- Type C: tyrosyl-tRNA synthetase gene mutation (YARS) causing localization of aminoacyl tRNA synthetase in granules of neuronal cells

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11
Q

What do mutations in RPS19 and/or RPS24 result in?

A
  • RPS19 is required for maturation of the 40S ribosomal subunit
  • RPS19 and 24 might be involved in binding eIF2
  • Mutations result in impairment of translation initiation; Diamond Blackfan anemia (DBA)
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12
Q

transformylase

A

the enzyme in prokaryotes that adds the formyl group onto the initiator Met–designated fMet-tRNA^fMet

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13
Q

How is eukaryotic initiator tRNA different from the rest?

A

The Met is not different from any other Met tRNAs, but when it is written out it is denoted: Met-tRNA^iMet

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14
Q

Shine-Dalgarno sequence

A
  • an A/G (purine)-rich sequence upstream of prokaryotic mRNA that (along with the TpsiC arm and codon-anticodon interaction) keeps the ribosomal subunit locked in place
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15
Q

VWM (Vanishing White Matter)

A
  • mutations in the eIF2B subunits resulting in
  • ataxia
  • CNS hypomethylation
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16
Q

Wolcott-Rallison Syndrome

A
  • mutation in PERK and therefore difficulties shutting down protein synthesis:
  • childhood diabetes mellitus (highest expression of PERK in beta cells) and therefore there may be difficulties shutting down insulin production beyond the capacity of the ER (and UPR?) and beta cell apoptosis
    NOTE:
  • mental retardation
  • hypothyroidism
  • dysfunctional liver, kidney, pancreas
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17
Q

Subsequent tRNAs that are added to the peptide chain are attached to ______ which helps them enter the ribosome

A

Prokaryotes: Tu-GTP
Eukaryotes: eEF1-alpha

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18
Q

After 2nd through last aas are added to the peptide chain, how are the EF-Tu-GTP/eEIFalpha regenerated for the next tRNA entry?

A

Prokaryotes: Tu-Ts
Eukaryotes: eEF1-beta-gamma

19
Q

Which non-RF releasing factors are involved in ribosome release (prokaryotes)?

A
  • EF-G (helps the ribosome translocate)
  • RRF (ribosome recycling factor)
  • IF-3: releases large subunit and therefore everything else
20
Q

Which RFs are involved in termination and what do each of them recognize?

A

Prokaryotes:

  • RF1: UAA and UAG
  • RF2: UAA and UGA
  • RF3: helps RF1 and RF2 work, also helps in ribosome dissociation (requires ATP)

Eukaryotes:

  • RF1: UAA, UAG, UGA
  • RF3: causes release of ribosome and hydrolyzes peptide
21
Q

What are mutations in the eEFs and what disease(s) do they cause?

A
  • no known mutations in these
22
Q

What are the mutations in eRF3?

A
  • GGC (Lys) expansion in gastric cancer
  • most common gives 10 gly’s and 12 gly form has been only seen in cancer patients
  • causes a 20-fold increase in risk of gastric cancer
23
Q

what causes mRNA misreading/blocks inititation?

A
  • streptomycin (changes 30S rRNA)
24
Q

What drugs block peptidyl transferases and therefore elongation?

A

Eukaryotes:
- cycloheximide: interferes with EF-G (a prokaryotic protein?)

Prokaryotes:
- chloramphenicol: inhibits peptide bond formation; last resort since it also works on mitochondria

25
Q

How does diptheria toxin work?

A

ADP-ribosylates eEF2 to stop translocation

26
Q

Erythromycin

A

prevents movement of ribosome along mRNA

28
Q

How can tRNA synthetases know which aa to put on a tRNA?

A
  • there are aa’s in the tRNA that are specific to the tRNA
28
Q

The site of the aminoacyl tRNA synthetase that does not do the proofreading is called _____

A

acylation site

29
Q

Which RNA is associated with the 30S subunit in prokaryotes?

A
  • 16S
30
Q

Which RNA is associated with the 50S subunit in prokaryotes?

A
  • 5S

- 23S

31
Q

Which RNA is associated with the 40S subunit in eukaryotes?

A
  • 18S
32
Q

Which RNA is associated with the 60S subunit in eukaryotes?

A
  • 5S
  • 5.8S
  • 28S
33
Q

(T/F) The RNA component of ribosomes takes up most of the nucleoprotein?

A

True–2/3

34
Q

What keeps the ribosomal subunit in place?

A
  • Shine Dalgarno sequence 5’ of mRNA
  • TpsiC sequence of tRNA
  • codon-anticodon binding
35
Q

Bind and Slide

A
  • mechanism by which eukaryotes initiate transcription
36
Q

How do eukaryotes initiate trascription?

A
  • eIF4 and 40S subunit binds 5’ cap
  • eIF2 binds 40S and brings Met
  • Complex slides to AUG
37
Q

eIF4

A
  • first binds cap of mRNA in eukaryotes

- helicase activity unwinds the RNA

38
Q

What regulates eukaryotic initiation?

A
  • eIF2B replaces the GDP for GTP to make eIF2 active

- PERK phosphorylates eIF2 to inactivate it

39
Q

What would you expect with mutations in eIF2B?

A
  • slow protein synthesis
40
Q

What would you expect with mutations in PERK

A

can’t shut down protein synthesis

41
Q

What catalyzes peptide bond formation?

A
  • Prokaryotes: 23S RNA

- Eukaryotes: 28S RNA

42
Q

Which proteins move the mRNA so the next codon is available?

A
  • Prokaryotes: EF-G
  • Eukaryotes: eEF2
    NOTE: both require GTP!
43
Q

Tetracycline

A

Interferes with tRNA anticodon reading

MHG - Exam I (11 decks)

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