Translation Process Flashcards
(108 cards)
1
Q
Translation process
A
- initiation
- elongation
- termination
2
Q
formation of a complex where the mRNA, ribosomes, and initiator tRNA form the translation machinery
A
initiation
3
Q
forms the translation machinery
A
- mRNA
- ribosomes
- initiator tRNA
4
Q
synthesis of peptide in a 3-step cycle that repeats each time an amino acid is added
A
elongation
5
Q
cycle in elongation
A
3-step cycle
6
Q
halting of translation upon encountering a stop codon
A
termination
7
Q
- ribosome-binding site in prokaryotes
- consensus 5’ AGGAGGU 3’
- 3-10 nucleotides upstream of the initiation codon
- complementary to a region at the 3’ end of the 16S RNA
A
Shine Dalgarno sequence
8
Q
consensus of Shine Dalgarno sequence
A
5’ AGGAGGU 3’
9
Q
location of Shine Dalgarno sequence
A
3-10 nucleotides upstream of initiation codon
10
Q
Shine Dalgarno sequence is complementary to where
A
3’ end of 16S RNA
11
Q
- usually AUG
- sometimes GUG or UUG
A
start/initiation codons
12
Q
other start codons in prokaryotes
A
- GUG
- UUG
13
Q
Prokaryotic initiation factors
A
- IF-1
- IF-2
- IF-3
14
Q
actively promotes dissociation of ribosomal subunits
A
IF-1
15
Q
IF-1 function
A
promotes dissociation of ribosomal subunits
16
Q
binds to 30S subunits to prevent re-association with 50S subunit
A
IF-3
17
Q
IF-3 function
A
binds to 30S subunits to prevent re-association with 50S subunit
18
Q
is a GTPase that directs the attachment of fmet-tRNA
A
IF-2
19
Q
IF-2 function
A
GTPase that directs attachment of fmet-tRNA
20
Q
- formulated methionine
- activated tRNA
A
fmet-tRNA
21
Q
prokaryotic translation: elongation
A
- aminoacyl-tRNA binding at A site
- peptide bond formation
- translocation from A to P site and from P to E site
22
Q
aminoacylation
A
EF-Tu with GTP
23
Q
EF-Tu
A
elongation factor-thermo unstable
24
Q
function of EF-Tu
A
brings aa-tRNA to ribosome during elongation
25
activates GDP to GTP
EF-Ts
26
enzyme involved in peptide bond formation
peptidyl transferase
27
translocation from A to P and P to E site
EF-G w/ GTP or translocase
28
what happens to GTP during translocation from A to P and P to E
cleaved and ribosome moves along mRNA
29
when any of 3 stop codons is reached
termination
30
creates UAG stop codon
amber mutation
31
where is amber mutation named after
Harris Bernstein (Bernstein = amber in German)
32
amber mutation
UAG
33
creates UAA stop codon
ochre mutation
34
ochre mutation
UAA
35
creates UGA stop codon
opal mutation
36
opal mutation
UGA
37
recognizes stop codons
release factor (protein)
38
different prokaryotic release factor
1. RF-1
2. RF-2
3. RF-3
39
recognizes UAG and UAA
RF-1
40
recognizes UGA and UAA
RF-2
41
assists RF1 or RF2
RF-3
42
what do RFs activate
hydrolysis of peptidyl chain from the tRNA
43
what are released from the ribosome once it reaches stop codon
polypeptide chain and tRNA
44
Prokaryotic translation inhibitors
1. tetracycline
2. streptomycin
3. erythromycin
4. chloramphenicol
5. puromycin
45
inhibits binding of tRNAs to ribosome
tetracycline
46
- changes shape of 30s and interferes with normal codon-anticodon pairing
- misreading
streptomycin
47
binds 50S and prevents translocation
erythromycin
48
binds 50S and inhibits peptidyl transferase activity
chloramphenicol
49
- resembles 3' end of aa-tRNA
- premature chain termination
puromycin
50
prokaryotic:
binding to ribosome subunits
- IF1
- IF3
51
eukaryotic:
binding to ribosome subunits
- eIF3
- eIF4C
- eIF6
52
prokaryotic:
- binding to mRNA
- initiator tRNA delivery
- displacement of other factors
IF2
53
eukaryotic:
- binding to mRNA
- eIF4B
- eIF4F
54
eukaryotic:
- initiator tRNA delivery
- eIF2
- eIF2B
55
eukaryotic:
- displacement of other factors
eIF5
56
difference between prokaryote and eukaryote initiation based on where ribosome is located
pro: directly on start codon
eu: indirectly locate start codon
57
facilitates prokaryotic initiation
Shine-Dalgarno sequence
58
absent in eukaryotes (initiation)
RBS (ribosome binding site)
59
what mechanism is involved in eukaryotic initiation
scanning mechanism starting at 5' cap
60
- formation of pre-initiation complex
- pre-initiation complex binds to 5' cap
- pre-init complex scans mRNA until it locates AUG
- start codon is usually contained in Kozak consensus
- once pre-init complex is properly positioned, 60S binds to form 80S initiation complex
The Scanning Model
61
pre-initiation complex
40S + met-tRNA + eIF2 + GTP
62
assists the binding of pre-init complex to 5'cap
- eIF3 and
- cap binding complex
63
cap binding complex
eIF4F
64
eIF4F
eIF4A + eIF4E + eIF4G
65
where is the start codon usually contained in
Kozak consensus
66
Kozak consensus
5' ACCAUGG 3'
67
The Scanning Model
1. formation of pre-initiation complex
2. pre-initiation complex binds to 5' cap
3. pre-init complex scans mRNA until it locates AUG. Start codon is usually contained in Kozak consensus
4. once pre-init complex is properly positioned, 60S binds to form 80S initiation complex
68
binds to form the 80S initiation complex
60S
69
what happens after 60S binds and forms 80S
- GTP hydrolysis
- release of eIFs
70
eukaryotic translation:
elongation
1. eEF-1α
2. eEF-1βγ
3. eEF-2
4. no E site in ribosome
71
eEF-1α : __ (prokaryotes)
EF-Tu
72
eEF-1βγ : __ (prokaryotes)
EF-Ts
73
eEF-2 : __ (prokaryotes)
EF-G
74
eukaryote:
- recognizes all 3 stop codons
- requires ATP
eRF1
75
function of eRF1
recognizes all 3 stop codons
76
- stimulates release of eRF1 from the ribosome after termination
- assists eRF1
eRF2
77
function of eRF2
stimulates release of eRF1 from ribosome after termination
78
Accuracy of Protein Synthesis
1. charging tRNA with correct aa
2. codon-anticodon
3. specific contacts between tRNA, mRNA, and rRNA within A site
4. proof-reading by rejecting an incorrect aminoacyl-tRNA before it can donate its aa
79
what is involved in protein targeting in eukaryotes
1. signal peptide
2. signal recognition particle (SRP)
80
found in the N-terminal of the nascent protein
signal peptide
81
immediate product of translation that is inactive
nascent protein
82
recognizes signal peptide
signal recognition particle (SRP)
83
what does the SRP do
- recognize signal peptide
- binds to ribosome to arrest translation
84
where does the SRP with arrested ribosome binds to
SRP receptor
85
where is the SRP receptor found
Cytosolic face of rough ER membrane
86
where the ribosome attaches to trigger the release of SRP
ribosome receptor protein
87
what happens when ribosome attaches to ribosome receptor protein
release of SRP for re-use
88
once, SRP is released, what happens to the ribosome
continues translation and nascent protein is pushed through rough ER's lumen
89
what happens as the nascent protein passes through the rough ER's lumen
signal peptidase cleaves off signal peptide
90
what happens to the protein inside the rough ER's lumen
glycosylated
91
control the final location of the protein
pattern of glycosylation
92
Events in Protein Targeting
1. SRP recognizes singal peptide, binds to ribosome to arrest translation
2. SRP with arrested ribosome binds to SRP receptor on cytosolic face of rough ER
3. ribosome attaches to ribosome receptor protein, triggers release of SRP
4. ribosome continues translation, nascent protein pushed through rough ER's lumen
5. as nascent passes through, signal peptidase cleaves off signal peptide
6. protein is glycosylated to control its final location
93
Some Post-Translational Modifications
1. glycosylation
2. hydroxylation
3. acetylation
4. phophorylation
94
addition of -OH group like in the formation of 4-hydroxyproline in collagen
hydroxylation
95
addition of -COCH3 group such as in histone proteins
acetylation
96
addition of -PO43- group in tyrosine, serine, and threonine residues
phosphorylation
97
- reversible
- activation/inactivation of enzyme activity
- modulation of molecular interactions
- signaling
phosphorylation
98
- protein stability
- protection of N terminus
- regulation of protein-DNA interactions (histones)
acetylation
99
regulation of gene expression
methylation
100
- cellular localizatio and targeting signals
- membrane tethering
- mediator of protein-protein interactions
acylation, fatty acid modification
101
- excreted proteins
- cell-cell recognition/signaling O-GlcNAc
- reversible
- regulatory functions
glycosylation (N-linked, O-linked)
102
protein stability and protein-ligand interactions
hydroxyproline
103
modulator of protein-protein and receptor-ligand interactions
sulfation (sTyr)
104
- intra- and intermolecular crosslink
- protein stability
disulfide bond formation
105
- possible regulator of protein-ligand and protein-protein interactions
- common chemical artifact
deamidation
106
- protein stability
- blocked N terminus
pyroglutamic acid
107
- destruction signal
- after tryptic digestion
- site is modifed with Gly-Gly dipeptide
ubiquitination
108
oxidative damage during inflammation
nitration of tyrosine
