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CBG PANT Replication, transcription and translation > CBG Lecture 7: Translation > Flashcards

CBG Lecture 7: Translation Flashcards

(73 cards)

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1
Q

what is the ribosome

A

a massive ribonuceloprotein with ribozymal peptidyl transferase activity

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2
Q

what Svedberg unit are bacterial ribosomes

A

70S

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3
Q

what Svedberg unit are eukaryotic ribosomes

A

80S

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4
Q

where does translation occur

A

on the ribosomes

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5
Q

what does translation require

A

ribosome

charged tRNA, mRNA GTP and variety of initiation, elongation and termination factors to ensure accurate synthesis

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6
Q

what do ribosomes do

A

translate the codons of the mRNA into the sequence on a protein

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7
Q

how many subunits in a ribosome? what are they called

A

2 subunits
Large subunit
Small subunit

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8
Q

what does SSU do

A

small ribosomal subunit

binds mRNA, ensures codon pairs correctly with anticodon

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9
Q

what does LSU do

A

large ribosomal subunit
AS peptidyl transferase found here
where aas are attached to make a protein

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10
Q

what is the catalytic site of a ribosome made of?called?

A

peptidyl transferase active site
made entirely of rRNA
its a ribozyme

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11
Q

what is the error rate for translation of eukaryotes/bacteria

A

10-4 per aa

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12
Q

which translates faster, E.coli or humans?

A

E.coli by 10 times

E.coli : 20aa per sec

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13
Q

in prokaryotes and euks where does translation occur

A

in cytoplasm

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14
Q

WHAt machine is used for translation

A

ribosome, ribozyme, LSU, SSU

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15
Q

how is translation initiated

A

Initiation factors recruit tRNAi to the P site on the naked SSU, expending GTP

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16
Q

how many sites are on the SSU?

A

3
E(xit site)
P(eptidyl tRNA site)
A(minoacyl tRNA site)

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17
Q

what does the E stand for on the SSU

A

exit site

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18
Q

what does P stand for on SSU

A

peptidyl tRNA site

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19
Q

what does the A stand for on SSU

A

aminoacyl tRNA site

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20
Q

what is initiatior tRNA charged with in bacteria and endosymbionts

A

formylmethionine

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21
Q

what is initiator tRNA charged with in eukaryotes and archaea

A

methionine

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22
Q

whereabouts is the adenosine in tRNA

A

at 3’ end

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23
Q

how is initiator tRNAi removed? when is it removed

A

removed by peptidase after translation

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24
Q

outline initiation for translational initiation (inc. elF etc)

A

elF3 prevents LSU binding
elF1 blocks A site
elF2 brings tRNAi to P site
expends GTP, hydrolysis GTP, releases IFs allows LSU to bind

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25
outline elFs and what they do in translational initiation
elF3- prevents LSU binding elF1 - blocks A site elF2 - brings tRNAi to P site, , hydrolysis GTP, releases IFs allows LSU to bind
26
what part of mRNA does the ribosome bind to first in eukaryotes
the methylguanosine 5' cap, then finds the first AUG after that the eukaryotic consensus (Kozac sequence) plays similar role to Shine-Dalgarno sequence but not as conserved
27
what does elF3 do
prevents LSU binding
28
what does elF1 do
blocks A(minoacyl tRNA) site
29
what does elF2 do
brings tRNAi to P(eptidyl tRNA) site, hydrolysis GTP, releases IFs allows LSU to bind
30
what is a Kozac sequence? what is it analogous to
eukaryotic consensus | similar role to SDS (Shine Dalgarno Seqeunce) but not as strongly conserved
31
how is the AUG in prokaryotes distinguished from other AUGs
by a Shine Dalgarno Sequence
32
why is AUG ambiguous in bacterial mRNA
because their mRNA is polycistronic, so AUG could be a start codon, inernal methionine or out of phase codon with reading frames
33
why do eukaryotic mRNAs not need an SDS
because its monocistronic, ribosome just needs to bind mRNA 5' cap then find the AUG after
34
what is the chance of getting an SDS sequence in polycistronic mRNA
1/262144
35
what is the chance of getting an AUG codon
1//64
36
what provides evidence for LUCA
genetic code is almost universal AUG is the typical start codon there are only a small number of variations of genetic code
37
how many GTPs are expended per aa in translational elongation what is it used for
2GTP/aa - energy intensive | transfers the peptidyl on the P site tRNApeptidyl to the A site tRNAaminoacyl
38
outline elongation factors and their roles used in translational elongation
EF1 brings charged tRNA to A site EF2 shunts ribosome along LSU catalyses peptide bond formation
39
what does AUG code for in bacteria? in eukaryotes?
AUG - methionine in euks | formylmethionine in proks
40
what can UGA also code for
selenocysteine instead of a stop
41
how does ribosome distinguish between whether something is a stop codon or codes for an aa
based on secondary structures in mRNA
42
how is the initiator aa removed from the mature protein
by a peptidase
43
what does tRNA wobble lead to
non-Watson-Crick pairing at 3' third base of codon
44
how many aas? how many tRNAs
20 aas | 40 tRNAs
45
what are stop codons bound by
release factors (tRNA peptidyl hydrolase) terminating translation
46
what does EF1 do
brings charged tRNA (eg. serine or threonine) to A site
47
name some charged tRNAs
serine threonine (have OH group)
48
what does EF2 do
shunts ribosome along - conformational change | uses GTP
49
what part of ribosome catalyses peptide bond formation
LSU
50
what does the LSU do
catalyses peptide bond formation
51
what part of translational elongation requires ATP
2 ATP to attach aminoacyl to the tRNA in first place | for every amino acid added = 4 ATP
52
how many GTPs and ATPs used during translational elongation
2GTP per AA | 4ATP per AA
53
how can mRNA convey meaning
through secondary structures eg. convert stop to selenocysteine (UGA) convert stop to pyrolysine (UAG)
54
what does UGA | UAG code for
UGA - stop/selenocysteine | UAG - stop/pyrolysine
55
how does mRNA convey meaning to ribosome about UGA/selenocysteine
converts STOP to selenocysteine by expending GTP | catalysed by a SEcIS : selenocysteine inserion element
56
what is a polyribosome array | what does it do
lots of ribosomes | acts on a elF4-coiled mRNA to increase efficiency of translation
57
how is protein folding detemined
by primary structure
58
what is a molten globule
native secondary structure by liquid interior
59
what is native state
the favoured entropic state but can get trapped in local energy minima
60
give some examples of disease caused by faulty protein folding
CF Marfan syndrome Creutzfeld Jakob disease Alzheimer's disease
61
how is CF caused
misfolding of transmembrane regulator
62
how is Margan syndrome caused
misfolding of fibrillin
63
how is Creutzfeldt Jakob disease caused
misfolding of prion protein due to extracellular aggregation
64
how is Alzheimer's disease caused
misfolding beta-amyloid due to extracellular aggregation
65
what does a stacked beta sheet in a misfolding prion to
catalyses the misfolding of other prions leading to an exponential fatal misfolding catastrophe
66
what are chaperonins
protein chaperones help fold proteins
67
where does protein folding take place - is it an active process? how does it work
inside barrel of GroEL/GroES chaperonin - uses ATP | exposed hydrophobic residues on outside of protein are relocated to inside of protein
68
what happens to unfoldable and unwanted proteins
theyre ubiquitinated and degraded in proteasomes
69
what are proteasomes
they ubiquitinate and degrade unfoldable and unwanted proteins
70
how do proteasomes ubiquitinate
attach a 5 ubiquitin tail to the waste protein
71
how many subunits are present in proteasome
2 regulatory subunit: recognises 5Ubiquitinated protein, deubiquitinates and unfolds it proteolytic subunit: degrades the protein
72
what does the regulatory subunit of a proteasome do
recognises 5 U ubiquitinated protein, de-Us it then unfolds it
73
what does the proteolytic subunit of a proteasome do
degrades the unwanted protein

CBG PANT Replication, transcription and translation (10 decks)

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