Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIOC2004 > 10 - Ribosomes and Cotranslation > Flashcards

10 - Ribosomes and Cotranslation Flashcards

1
Q

What part of the ribosome is responsible for the translation reaction itself, and what are its components?

A

The peptidyl transferase centre is made up of the E, P and A sites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the subunit makeup of the prokaryotic ribosome.

A

A 70S complex made up of a 50S and a 30S subunit that bind over the mRNA and hence both contain parts of the peptidyl transferase centre.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the total mass of 70S prokaryotic ribosome?

A

2.5MDa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the relative proportion or rRNA to protein in the 70S ribosome?

A

65% rRNA

35% protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What have been the most useful tools for elucidating the ribosome structure?

A

Cryo-EM and XRD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the molecular mass of the 30S subunit?

A

0.8MDa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the molecular mass of the 50S subunit?

A

1.5MDa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How many proteins are attached to the 30S ribosome?

A

21

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How many base pairs of rRNA are present within the 30S ribosome?

A

1.5Mbp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the sedimentation coefficient of the 30S subunit after all the proteins have been removed?

A

16S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the function of the 30S subunit?

A

It is the first to bind to the mRNA, which enters and exits the ribosome through it. It is hence responsible for recruitment and jointly responsible for the fidelity due to its large role in facilitating the m-tRNA interaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How many rRNA chains are present in the 30S subunit?

A

1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How many rRNA chains are present in the 50S subunit?

A

2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How many proteins are attached to the 50S ribosome?

A

34

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the sedimentation coefficients of the isolated 50S subunit rRNA chains?

A

5S and 23S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the total number of base pairs of rRNA present in the 50S subunit?

A

3Mbp

17
Q

What is the function of the 50S subunit?

A

Contains the peptidyl transferase centre, so is reponsible for catalysing peptide bond formation.
Also contains the peptide exit tunnel.

18
Q

What is the rate of peptide bond formation in a 70S ribosome?

A

20 per second.

19
Q

How long is the ribosomal exit tunnel?

A

100A

20
Q

What is the widest diameter of the ribosomal exit tunnel?

A

20A

21
Q

What rRNA and protein components make up the ribosomal exit tunnel?

A

23S subunit and proteins L4 and L22.

22
Q

What property of the ribosomal exit tunnel prevents interaction with the nascent peptide?

A

It is lined with hydrophilic residues.

23
Q

What delivers the tRNA to the active site?

A

EF-Tu GTP

24
Q

If the tRNA delivered has a matching anticodon to the mRNA codon, what happens?

A

This causes an rRNA conformation change, which spins the tRNA by 5°, but not yet into the A site.
There is also domain closure of the 30S subunit shifting the EF-Tu GTP into position.

25
Q

What happens when match identification causes the EF-Tu GTP to assume its active position?

A

The GTP is hydrolysed leading to a 100° change in conformation of the EF-Tu causing it to dissociate.
This also powers the entry of the tRNA into the A site.

26
Q

How are the arms of the tRNA molecules named?

A 
Acceptor arm (binds AA)
Anticodon arm
C, D and T arms.
27
Q

How much structure forms in the ribosomal exit tunnel?

A

It is only wide enough to allow for some limited helical structure to develop.

28
Q

Which protein is a common model for cotranslational folding, and why?

A

Luciferase, as it is unable to fold under any other circumstances.

29
Q

How does luciferase fold?

A

Exclusively cotranslationally, as the N-terminal domain folds as it exits around which the rest of the protein folds.. Hence unlike RNaseA it would not refold if denatured.

30
Q

How can cotranslational folding be imaged?

A

By removing the stop codon from a gene in order so that it doesn’t recruit release factors and hence gets stuck in the ribosome.

31
Q

What protein production technique is often used to image ‘folding snapshots’ from cotranslational folding?

A

Cell-free expression, as this allows for easy purification.

32
Q

What imaging technique is used to view cotranslational folding?

A

NMR, as this allows continuous visualisation of the folding process as it, uhh… unfolds, as opposed to a still snapshot.

33
Q

How can snapshots of cotranslational folding at different points be taken?

A

By lengthening and shortening the gene artificially to change where it stalls and hence which bit of the nascent chain is protruding from the ribosomal exit tunnel.

34
Q

What is example of a protein whose N-terminal domains begin folding before the others have exited the ribosomal exit tunnel?

A

Ig2 antibodies. The first domain begins folding before even all of that has exited, and continues more after 37AAs of the linker region between the 106AA Ig domain is translated and the first domain is fully folded at a linker length of 89AA.

35
Q

How is NMR usually used to produce an image of the nascent protein?

A

By using N-15 tagged amino acids in the translation.

36
Q

How is the folding of ubiquitin thought to occur?

A

Beginning within the ribosomal exit tunnel.

BIOC2004 (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions