Key Terms with Example Questions Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

ubiquitin

A

a 76 amino acid polypeptide that acts as a tag to identify misfolded, obsolete, and damaged proteins to be degraded by proteases or repaired by polyubiquitylation,
depending on whether it binds to lys 48 for degradation or lys 63 for repair

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

proteasome

A

has 3 parts (2 19s cap and 20s core)

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

chaperonin

A

Hsp60; a class of chaperones that act post-translationally and facilitate folding by their small chamber

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

degron

A

a sequence that marks a target protein as needing to be degraded; a signal to E3

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

hsp 70

A

aka HSC (heat shock cognate); acts co-translationally and functions to bind and stabilize unfolded/partly folded proteins to prevent aggregation while the new protein is still being translated because it does not know how to fold until fully synthesized;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q
  • E3
A

ubiquitin ligase; attaches to the degron of a target protein to transfer ubiquitin from E2 to the lysine48 NH3 group, resulting with the polyubiquitin chain on the target protein

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

20s core

A

protease; has the active sites to clip every peptide bond and keeps the entire substrate bound until it is converted into amino acids

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

ubiquitin conjugating enzyme

A

E1; has a cysteine side chain (-SH) that attaches to ubiquitin (COO-) to form a thioester bond (S-C=O)

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

target protein

A

a protein that is marked or needs to be marked for either degradation, repair, etc.

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

For further thought: There are about 600 E3 ligases and 30 distinct E2 molecules. Why do you think there is such a big difference in the number of E3 and E2 molecules?

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

Application: Components of the ubiquitin machinery were identified independently in genetic screens for genes that regulate the cell cycle. A mutation in genes required for chromosome segregation should cause cells to arrest in mitosis before chromosome segregation occurs. As it turns out, in some of these mutants that arrested in mitosis before chromosome segregation, the gene product was required for proteolytic destruction of specific proteins. What do you think these specific proteins do? What does the unmutated form of the gene encode?

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

In your own words describe the overarching cell biology concept illustrated by these pathways?

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

Ubiquitin can also regulate histones by

A

monoubiquitylation and endocytosis by multiubiquitylation; attaches as a tag by an isopeptide bond

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

Ubiquitin receptor on 19s cap…

A

recognizes ubiquitin

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

Ubiquitin hydrolase on 19s cap…

A

clips ubiquitin

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

hexameric unfoldase ring on 19s cap…

A

unwinds protein strand by stretching and pulling the substrate by ATP hydrolysis; protein moves to 20s core (protease) that keeps the substrate bound until all peptide bonds are cut by active sites; amino acids exit the bottom 19s cap to re-assist the cell

17
Q

Hsp 60 functions to prevent…

A

aggregation by having a high affinity for the nonpolar side chains sticking out of the misfolded/incomplete proteins by binding and pulling them in

18
Q

Hsp 60 is capped by… with what in the cap…

A

GroEL/GroES; with ATP and the cap

19
Q

Hsp60 elongates to…

A

stretch and properly fold the protein

20
Q

Hsp 60 properly folded then what happens??

A

ADP is released and with the addition of another ATP, the cap is off and the newly folded protein is released

21
Q

activating the degron has different pathways: what are they??

A

phosphorylation by kinases, unmasked by protein dissociation, and creation of a destabilizing N-terminus

22
Q

Hsp 70 binds to

A

the SBD 9 substrate binding domain) on the nonpolar side chains with ATP (which is bound by the nucleotide binding domain); as ATP is hydrolyzed to ADP, SBD clamps down, folding the protein, and releases as new ATP s added