MCB Exam 3 Exam Questions and Answers 100%
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what are the factors that keep the small eIF3 keeps the small subunit from binding the large to the
ribosomal subunit from binding the large large subunit in translation
ribosomal subunit?
differences between translational Prok:
initiation in prok and euk -initiation factors IF1 and IF3 are initially bound to 30S subunit
-mRNA, initiator fMet, and IF2/GTP join complex
-IF1 and IF3 released and 50S subunit binds
-binding of 50S triggers hydrolysis of IF2/GTP to IF2/GDP,
which is then released
Euk:
-eIF1, eIF1A, and eIF3, and eIF5 bind to 40S subunit
-eIF3 keeps subunits apart
-Met tRNA is then brought to P site in complex by eIF2/GTP
-mRNA brought to 40S subunit by eIF4E (binds to 5' cap)
-eIF4G (bound to eIF4E), eIF4A, and eIF4B come complexed
with eIF4E
-ribosome scans down mRNA to identify Kozaks seq.
-AUG identified, eIF5 triggers hydrolysis of eIF2/GTP followed
by release of eIF2/GDP
-all factors fall off except Met tRNA and eIF1A
-eIF1A binds eIF5B/GTP which binds the large subunit
-binding of large subunit triggers hydrolysis of eIF5B/GTP
-eIF5B/GDP and eIF1A fall off leave A site open for translation
IF2/GTP - role in process IF2/GTP interacts with the initiator tRNA (methionyl tRNA) and
brings it to the P site
,met-tRNA - why is Met always the first it is the only one that has the ability enter easily into the P
amino acid used to start translation in euk site of the small ribosomal subunit
cells?
all other tRNAs enter ribosome through the A site
eIF2/GTP - role in translational initiation eIF2/GTP is a GTPase that binds to initiator methionyl tRNA
and recognizes start site by the tRNA
besides keeping small ribosomal subunit recruits eIF5 and and eIF1, and allows 43S complex to
away from the large, what else does associate with eIF4G, therefore leading to the formation of the
eIF3 do? 48S pre-initiation complex
indicate the role of each of the following -eIF5: triggers hydrolysis of eIF2/GTP
initiation factors: eIF5, eIF1A, eIF1, eIF5B -eIF1A: binds to A site to block binding of any other tRNA and
binds eIF5B/GTP
-eIF1: binds to 40S ribosomal subunit
-eIF5B: a GTPase that binds to eIF1A and recruits large subunit
to be bound to complex
factors that activate the mRNA - what do all -PABP: poly-adenyl binding protein; associated with the poly-
of them do? A tail at the 3' end of mRNA and stimulates translation by
(PABP, eIF4G, eIF4E, eIF4A and eIF4B) interacting with eIF4G
-eIF4G: (remember G=grouping) eIF4G interacts with eIF3;
binds to PABP; one of the initiation factors; in association
with eIF4A and eIF4B and eIF4E, brings mRNA to 40S
ribosomal
subunit
-eIF4E: recognizes and binds to 5' cap of mRNA and forms
complex with eIF4G and eIF4A
-eIF4A and eIF4B: bind to eIF4G; only work if they are
together; in association with initiation factors eIF4E and eIF4G,
they bring mRNA to the 40S subunit with eIF4G interacting
with eIF3
whats the collective name assigned to eIF4F
eIF4E, eIF4G, eIF4A and eIF4B?
whats the role of the 5' cap and the 3' poly A the 5' cap and 3' poly A tail ensure mRNA stability; 5'
tail on translation initiation? cap required for translation, while 3' poly A tail only
enhances translation (not necessary)
why does scanning require ATP hydrolysis? because of the need to provide energy for the helicase
activity mediated by eIF4A and eIF4B
whats the signal that triggers disassembly when eIF2/GTP hydrolyses GTP to GDP, triggering a
of the 48S pre-initiation complex? conformational change in eIF2 that results in the disruption
of the 48S pre-initiation complex
whats the factor that activates the GTPase eIF5
activity of eIF2? -after kozaks sequence is identified and tRNA clicks in place
, whats the role of eEF1alpha? eEF1alpha/GTP is a GTPase that escorts the initiating
aminoacyl tRNA (ex. alanyl tRNA) to the ribosome
-a peptide bond is formed btw the Met and Ala
after it is hydrolyzed to eEF1alpha/GDP it leaves ribosome
with alanyl tRNA inserted into A site
-bonded Met and Ala move to P site leaving A site open
whats the name of different regions in the E, P, A
ribosome that are involved in tRNA binding?
what does each of those mean? E: exit site
P: peptidyl site
A: aminoacyl site
whats the role of eEF2? mediates translocation (movement of Met-Ala trNA to the P
site and uncharged trNA to the E site , leaving an empty A site
ready for addition of next amino acid)
whats involved in creating a new peptide once eEF1alpha has left the ribosome, a peptide bond can be
bond? formed between initiator Met tRNA at the P site and the
second aminoacyl tRNA at the A site
-insertion of a correct amino acyl tRNA into the A site triggers
a conformational change that induces hydrolysis of GTP
bound to eEF1alpha
-release of eEF1alpha/GDP
how is GTP-loaded (or bound) eEF1alpha eEF1alpha/GDP released from ribosome must be reconverted
recycled? whats the name of the GTP to its GTP form; done by binding of GTP exchange factor
exchange factor for this process? to
eEF1alpha/GDP and promotes exchange of bound GDP for
GTP
this GTP exchange factor is called eEF1βγ
polysomes vs. monosomes - why does it polysomes: mRNAs that are translated by a series of multiple
matter? whats a polysome? what are ribosomes
they spaced at? -spaced at about 100 to 200 nucleotides
it is important because a single mRNA molecule can be
translated simultaneously by several ribosomes in both prok
and euk cells
is there translational regulation in bacteria? since in bacteria, transcription and translation occur
why? simultaneously, most of the regulation occurs
transcriptionally but it IS possible to have translational
regulation
mechanisms by which translational 1) binding of repressor proteins to specific mRNA
regulation can be achieved - which ones are sequence: (specific to one transcript)
global and which are specific to one
transcript? 2)binding of proteins to specific sequences in the 3' UTR of
some mRNAs: (specific to one transcript)
3) modulation of the activity of initiation factors: (global)
Guaranteed Success | Already Rated A+
Students also studied
Flashcard sets Study guides
C
Terms in this set (180)
what are the factors that keep the small eIF3 keeps the small subunit from binding the large to the
ribosomal subunit from binding the large large subunit in translation
ribosomal subunit?
differences between translational Prok:
initiation in prok and euk -initiation factors IF1 and IF3 are initially bound to 30S subunit
-mRNA, initiator fMet, and IF2/GTP join complex
-IF1 and IF3 released and 50S subunit binds
-binding of 50S triggers hydrolysis of IF2/GTP to IF2/GDP,
which is then released
Euk:
-eIF1, eIF1A, and eIF3, and eIF5 bind to 40S subunit
-eIF3 keeps subunits apart
-Met tRNA is then brought to P site in complex by eIF2/GTP
-mRNA brought to 40S subunit by eIF4E (binds to 5' cap)
-eIF4G (bound to eIF4E), eIF4A, and eIF4B come complexed
with eIF4E
-ribosome scans down mRNA to identify Kozaks seq.
-AUG identified, eIF5 triggers hydrolysis of eIF2/GTP followed
by release of eIF2/GDP
-all factors fall off except Met tRNA and eIF1A
-eIF1A binds eIF5B/GTP which binds the large subunit
-binding of large subunit triggers hydrolysis of eIF5B/GTP
-eIF5B/GDP and eIF1A fall off leave A site open for translation
IF2/GTP - role in process IF2/GTP interacts with the initiator tRNA (methionyl tRNA) and
brings it to the P site
,met-tRNA - why is Met always the first it is the only one that has the ability enter easily into the P
amino acid used to start translation in euk site of the small ribosomal subunit
cells?
all other tRNAs enter ribosome through the A site
eIF2/GTP - role in translational initiation eIF2/GTP is a GTPase that binds to initiator methionyl tRNA
and recognizes start site by the tRNA
besides keeping small ribosomal subunit recruits eIF5 and and eIF1, and allows 43S complex to
away from the large, what else does associate with eIF4G, therefore leading to the formation of the
eIF3 do? 48S pre-initiation complex
indicate the role of each of the following -eIF5: triggers hydrolysis of eIF2/GTP
initiation factors: eIF5, eIF1A, eIF1, eIF5B -eIF1A: binds to A site to block binding of any other tRNA and
binds eIF5B/GTP
-eIF1: binds to 40S ribosomal subunit
-eIF5B: a GTPase that binds to eIF1A and recruits large subunit
to be bound to complex
factors that activate the mRNA - what do all -PABP: poly-adenyl binding protein; associated with the poly-
of them do? A tail at the 3' end of mRNA and stimulates translation by
(PABP, eIF4G, eIF4E, eIF4A and eIF4B) interacting with eIF4G
-eIF4G: (remember G=grouping) eIF4G interacts with eIF3;
binds to PABP; one of the initiation factors; in association
with eIF4A and eIF4B and eIF4E, brings mRNA to 40S
ribosomal
subunit
-eIF4E: recognizes and binds to 5' cap of mRNA and forms
complex with eIF4G and eIF4A
-eIF4A and eIF4B: bind to eIF4G; only work if they are
together; in association with initiation factors eIF4E and eIF4G,
they bring mRNA to the 40S subunit with eIF4G interacting
with eIF3
whats the collective name assigned to eIF4F
eIF4E, eIF4G, eIF4A and eIF4B?
whats the role of the 5' cap and the 3' poly A the 5' cap and 3' poly A tail ensure mRNA stability; 5'
tail on translation initiation? cap required for translation, while 3' poly A tail only
enhances translation (not necessary)
why does scanning require ATP hydrolysis? because of the need to provide energy for the helicase
activity mediated by eIF4A and eIF4B
whats the signal that triggers disassembly when eIF2/GTP hydrolyses GTP to GDP, triggering a
of the 48S pre-initiation complex? conformational change in eIF2 that results in the disruption
of the 48S pre-initiation complex
whats the factor that activates the GTPase eIF5
activity of eIF2? -after kozaks sequence is identified and tRNA clicks in place
, whats the role of eEF1alpha? eEF1alpha/GTP is a GTPase that escorts the initiating
aminoacyl tRNA (ex. alanyl tRNA) to the ribosome
-a peptide bond is formed btw the Met and Ala
after it is hydrolyzed to eEF1alpha/GDP it leaves ribosome
with alanyl tRNA inserted into A site
-bonded Met and Ala move to P site leaving A site open
whats the name of different regions in the E, P, A
ribosome that are involved in tRNA binding?
what does each of those mean? E: exit site
P: peptidyl site
A: aminoacyl site
whats the role of eEF2? mediates translocation (movement of Met-Ala trNA to the P
site and uncharged trNA to the E site , leaving an empty A site
ready for addition of next amino acid)
whats involved in creating a new peptide once eEF1alpha has left the ribosome, a peptide bond can be
bond? formed between initiator Met tRNA at the P site and the
second aminoacyl tRNA at the A site
-insertion of a correct amino acyl tRNA into the A site triggers
a conformational change that induces hydrolysis of GTP
bound to eEF1alpha
-release of eEF1alpha/GDP
how is GTP-loaded (or bound) eEF1alpha eEF1alpha/GDP released from ribosome must be reconverted
recycled? whats the name of the GTP to its GTP form; done by binding of GTP exchange factor
exchange factor for this process? to
eEF1alpha/GDP and promotes exchange of bound GDP for
GTP
this GTP exchange factor is called eEF1βγ
polysomes vs. monosomes - why does it polysomes: mRNAs that are translated by a series of multiple
matter? whats a polysome? what are ribosomes
they spaced at? -spaced at about 100 to 200 nucleotides
it is important because a single mRNA molecule can be
translated simultaneously by several ribosomes in both prok
and euk cells
is there translational regulation in bacteria? since in bacteria, transcription and translation occur
why? simultaneously, most of the regulation occurs
transcriptionally but it IS possible to have translational
regulation
mechanisms by which translational 1) binding of repressor proteins to specific mRNA
regulation can be achieved - which ones are sequence: (specific to one transcript)
global and which are specific to one
transcript? 2)binding of proteins to specific sequences in the 3' UTR of
some mRNAs: (specific to one transcript)
3) modulation of the activity of initiation factors: (global)
