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CMB2001 > Translation > Flashcards

Translation Flashcards

1
Q

what occurs in the cleft of tRNA synthetase

A
  • glycine gains AMP from a ATP molecule - aminoacyl-adenylate
  • this then binds to a tRNA molecule which produces aminoacyl-tRNA
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2
Q

what are the positions in mRNA which are used by tRNA 30S subunit

A

Aminoacylated tRNA binding site (A)
Polypeptide chain site (P)
Exit site (E)

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3
Q

how is a peptide bond formed during translation elongation

A
  • a protein chain attached to the original tRNA is attached to the P site
  • A ‘charged’ tRNA binds to the A site
  • Then a peptide bond is formed
  • The protein chain is shifted to the newest tRNA (P site) by Elongation factor G (GTP) which binds to A site
  • Old tRNA is moved to the E site and released
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4
Q

what occurs to elongation factor G when it binds to A site

A

GTP -> GDP

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5
Q

what is elongation factor G in eukaryotes

A

eEF2

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6
Q

how does the 5’CAP initiate translation

A

Small subunit binds the CAP, then scans/move to the first AUG -encoding the initiating methionine

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7
Q

what is the most frequently found sequence around the AUG in eukaryotic mRNA called

A

Kozak consensus sequence

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8
Q

what are the function of elF4E subunit of the eIF4F complex

A

m7G binding

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9
Q

what are the function of elF4G subunit of the eIF4F complex

A

binds eIF4E,A,3 PABP

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10
Q

what are the function of elF4A subunit of the eIF4F complex

A

ATPase, RNA helicase

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11
Q

what are the proteins needed for mRNA circularisation

A

eIF4E, G & PAB

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12
Q

What is the first step of Translation initiation

A
  • Ribosome recycling
    -> ABCE1, eIF3, eIF1A, EIF1
  • 40S subunit is formed
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13
Q

what is the 2nd step of translation initiation

A

eIF2 ternary complex formation
-eIF2 which contains GTP binds to Met-tRNA

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14
Q

what is the 3rd step of translation initiation

A

43S preinitiation complex is formed where the 2 complex made in step 1 and 2 join

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15
Q

what is the 4th step of translation initiation

A

attachment of 43S complex to activated mRNA (eIF4F complex already bound)

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16
Q

what is the 5th step of translation initiation

A

5’ to 3’ scanning

17
Q

what is the 6th step of translation initiation

A
  • Initiation codon recognition hydrolysis of eIF2-bound GTP and Pi release
  • 48S initiation complex formed
18
Q

what is the 7th step of translation initiation

A

Subunit joining and factor displacement
- 60S + eIF5B (joined to GTP) join
- eIF2(+GDP), eIF5, eIF3, eIF1 is displaced

19
Q

what is the 8th step of translation initiation

A

Hydrolysis of eIF5B-bound GTP and release of eIF5B and eIF1A

20
Q

what is the final product of translation initiation

A

80S initiation complex

21
Q

How is translation terminated

A
  • eRF1 binds to A site
  • eIF3, eIF1, eIF1A and ABCE1 is released
  • the ribosome is separated in 60S and 40S and mRNA and tRNA is released
22
Q

what is regulatory element of translation

A

eIF2B subunit of the eIF2

23
Q

how does eIF2B carry out its function

A

its level governs level of active eIF2-GTP and thus overall initiation rate

24
Q

eIF2B is down-regulated and phosphorylated in

A
  • response to stresses such as viral infection, amino acid deprivation
    -diabetic muscle
    -heavy metals
25
Q

how is eIF2B activated

A

Insulin
growth signals

26
Q

what regulates the expression of both Fe storage and transport proteins

A

levels of Fe

27
Q

what are UTR and where are they found

A

Untranslated regions
5’UTR - between CAP and AUG
3’UTR - between stop codon and polyA tail

28
Q

what occurs in low iron in terms of storage

A

IRP1/2 binds to 5’UTR causing translational repression

29
Q

what occurs in low iron in terms of transport

A

IRP1/2 binds to 3’UTR in both TfR1 and DMT1 whihc causes mRNA stabilisation

30
Q

what occurs to iron storage in high iron

A

4Fe-4s binds to IRP1 and IRP2 is degraded in the 5’UTR which causes translational activation

31
Q

what occurs to iron transport in high iron

A

4Fe-4s binds to IRP1 and IRP2 is degraded as well as degradation of probes using RNase in 3’UTR
This causes mRNA degradation

32
Q

what is TfR1B

A

Canonical Iron response element

33
Q

what are IRE with additional 5’ or 3’ unpaired nucleotides

A

L-ferritin, DMT1 and HIF-2a

34
Q

IRP1 is a _ protein

A

bifunctional

35
Q

In absence of iron IRP1 functions as

A

an iron responsive protein 1

36
Q

In the presence of Fe and Fe-S cluster assembly enzymes IRP1 turns into

A

c-aconitase which interconverts citrate and isocitrate

CMB2001 (11 decks)

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