Molecular Bio (Exam 4): Translation

In bacteria, what is the large and small ribosomal subunits?

small: 30S;

large: 50S.

In eukaryotes, what is the large and small ribosomal subunits?

small 40S;

large: 60S.

Ribosomes of ________ are different from 80S ribosome.

organelles.

The stage in translation including all processes before forming the peptide bond between the first two amino acids of the protein.

initiation.

The fastest step in translation; also known as translocation.

elongation.

The stage in translation involving the release of polypeptide and ribosome dissociation.

termination.

Although initiation, elongation, and termination are general concepts in both prokaryotic and eukaryotic systems, the ________ mechanism is very different between the two.

initiaiton.

Initiation in bacteria needs ____ subunits and accessory factors/

30S.

________ in bacteria needs 30S subunits and accessory factors.

initiation.

In E. coli, ribosome and what subunits subunits are in free pool are in equilibrium?

30S/50S.

In E. coli, 30S subunit with ________ ________ binds to mRNA first, and then 50S is recruited.

initiation factors (IFs).

Which subunit is recruit first to mRNA in E. coli?

30S subunit (with IFs).

Ribosome assembly on mRNA requires what?

IFs.

IFs are released upon 50S binding to 30S, and play no roles in ________.

elongation.

When are IFs released?

after 50S binding to 30S.

What two ways can the ribosome be released?

free or as subunits.

IFs are found only on what subunit?

30S.

What are the IFs in E. coli (required for initiation)?

IF-1, -2, -3.

Which IF binds to initiator tRNA and brings it to the P site element in 30S subunit/mRNA complex?

IF-2.

Which IF has GTPase activity, which is activated when 50S comes in?

IF-2.

Which IF binds to near A site element and prevents aminoacyl-tRNA from entering?

IF-1.

Which IF has multiple functions?

IF-3.

Which IF stabilizes free 30S subunits (controls equilibrium between ribosomal states)?

IF-3.

Which IF enables 30S to bind to mRNA and prevents it from binding to 50S?

IF-3.

Which IF checks the accuracy of recognition of the first aminoacyl-tRNA (initiator tRNA)?

IF-3.

Which IF guides initiator tRNA to P site by blocking E site?

IF-3.

Which IF must be released to allow 50S subunits to join the 30S/mRNA?

IF-3.

Translation starts with a ________ amino acid usually coded by AUG.

methionine.

Different ________ tRNAs are involved in initiation.

methionine.

The ________ tRNA has unique structural features.

intiator.

In initiator tRNA. there is no ________ ________ of the first base at the 5’ end.

base pairing.

In initiator tRNA, __ G-C pairs in the stem preceding the anticodon loop, allowing direct entry to P site.

3.

Initiator tRNA has formylated ________ ________, to increase its affinity to IF-2.

amino acid.

Prokaryotic and eukaryotic ________ tRNAs share common features.

initiator.

mRNA binds a 30S subunit to create the binding site for a complex of IF-2 and ________.

fMet-tRNA.

In E. coli, 30S binds to ribosome binding site composed of ________-________ sequence and AUG.

Shine-Dalgano.

In the context of ribosome binding Shine-Dalgano, the AUG is placed at the partial __ site.

P.

Shine-Dalgano sequence is complementary to the 3’ end of ___ rRNA.

16S.

Accessory factors distinguish ________ tRNA and regular tRNAs.

initiator.

IF-2 specifically binds to what?

fMet-tRNA.

EF-Tu (elongation factor) specifcally binds to tRNAs charged with regular ________ ________.

amino acids (Met-tRNAm).

What does not bind to fMet-tRNA.

EF-Tu (elongation factor).

IFs are not present during ________.

elongation.

Small subunits scan for initiation sites on ________ mRNA.

eukaryotic.

In eukaryotic mRNA, ________ subunit binds to methylated cap.

small.

Eukaryotic 40S subunits bind to the 5’ end of mRNA and scan the 5’____ until they reach the initiation site.

UTR.

For eukaryotic mRNA, during the 40S subunit scanning on mRNA, ________ structure should be resolved.

secondary.

In eukaryotic mRNA, an initiation site consists of a ________ consensus sequence.

Kozak.

In some viruses, 40S directly jump to a start codon instead of scanning, called ________ ________.

ribosome shunting.

In some viruses, the ribosome binds directly to an internal secondary structure in 5’UTR containing AUGH, the ________ ________ ________ site (IRES).

internal ribosome entry site.

Initiation factors are required for all stages of ________, including: binding the initiator Met-tRNA, 40S subunit attachment to mRNA, movement along mRNA, joining of 60S subunit.

initiation.

In eukaryotes, eIF2 binds to the Met-tRNAi and ________.

GTP.

eIF4E binds ___ ____.

5’ cap.

eIF4A (RNA helicase) melts ________ ________.

secondary structure.

eIF4G links 5’ and 3’ end by binding ________ and ________.

eIF4E and PABP.

What scans mRNA until AUG codon is found in eukaryotes?

48S preinitiation complex.

The last step of eukaryotic initiation is the ________ subunit joins.

60S (large).

An aminoacyl-tRNA brings an amino acid to ribosome and enters the ___ site.

A.

Peptidyl-tRNA is bound in the ___ site.

P.

Deacylated tRNA exits via the ___ site.

E.

An amino acid is added to the polypeptide chain by transferring the polypeptide from peptidyl-tRNA in the ___ site to aminoacyl-tRNA in the ___ site.

P; A.

A & P sites occupy both the ________ of ribosome.

subunits (small; large).

Ribosome moves by a codon via _________.

translocation.

Which is a monomeric G protein whose active form (GTP bound) binds aminoacyl-tRNA?

EF-Tu.

The EF-Tu-GTP-aminoacyl-tRNA ternary complex binds to the ribosome ___ site.

A site (P site is occupied).

Once codon-anticodon base-pairing is complete in ____, Tu hydrolyzes GTP and tRNA occupies A site in 50s.

30S.

Tu-GDP is converted to Tu-GTP by what?

EF-Ts.

The large ribosomal subunit (50S or 60S) has _________ _________ activity.

peptidyl transferase.

The ascent polypeptide chain is transferred from peptidyl-tRNA in the __ site to aminoacyl-tRNA in the ___ site.

P; A.

The nascent polypeptide chain being transferred from peptidyl-tRNA in the P site to aminoacyl-tRNA in the A site, which is a function of what?

rRNA.

Peptide bond synthesis generates _________ tRNA in the P site and peptidyl-tRNA in the A site.

deacetylated.

Which two rRNAs play active roles in translation?

16S; 23S.

Which rRNA plays an active role in the functions of the 30S subunit?

16S.

Which rRNA interacts directly with mRNA, 23S rRNA in the 50S subunit (ribosome assembly0, and with the anticodon regions of tRNAs in P and A site?

16S rRNA.

Which rRNA interacts with the CCA terminus of peptidyl-tRNA in both P and A site?

23S rRNA.

Peptidyl transferase activity resides in the ____ rRNA in 50S subunit but not proteins.

23S.

Elongation factors bind alternatively to the _________.

ribosome.

Translocation requires ______, whose structure resembles the aminoacyl-tRNA-EF-Tu-GTP complex.

EF-G.

Which elongation factor is a monomeric GTPase?

EF-G.

Binding of EF-Tu and EF-G to the ribosome is _________ _________.

mutually exclusive.

Translocation requires _________ _________ ,which triggers a change in EF-G, which in turn triggers a change in ribosome structure.

GTP hydrolysis.

Kirromycin and fusidic acid block release of _________ and _________ respectively.

EF-Tu; EF-G.

Which mutation creates a stop codon?

nonsense mutation.

What are termination codons recognized by instead of aminoactyl-tRNAs?

class 1 release factors (RFs).

Which release factor recognizes UAA and UAG?

RF1.

Which release factor recognizes UAA and UGA?

RF2.

Which release factor recognizes all three stop codons?

eRF1.

What competes for A site?

EFs and RFs.

The structures of what resemble tRNA and C-terminal domain of EF-G?

class 1 RFs.

Class 1 RFs only bind to A site when __ site is occupied.

P.

Class 2FR is what kind of protein?

GTP-binding protein.

Class 2 RF facilitates dissociation of what from ribosome?

class I RFs.

Termination reaction releases the polypeptide but leaves a _________ tRNA and mRNA still associated with the ribosome.

deacylated.

_________ _________ _________ along with EF-G dissociate ribosome and uncharged tRNA.

Ribosome recycling factor (RRF).

RRF mimics _____, except that it lacks an equivalent for the 3;’ amino acid-binding region.

tRNA.

Translation can be regulated by the 5’ ______ of the mRNA.

UTR.

An example of translation being regulated by the 5’ UTR of mRNA include variation of these sequences.

Shine-Dalgano or Kozak sequences.

An example of translation being regulated by the 5’ UTR of mRNA include stability of ________ structure.

secondary.

Translation can be regulated by the abundance of various ______.

tRNAs.