L18

Question 1

____mg/mL protein

Answer 1

400mg/mL protein

Question 2

Avg protein

1. ___nm diameter
2. ____ nm space btwn

Answer 2

Avg protein

1. 6 nm diameter
2. 7 nm space btwn

Question 3

The different paths to the folded state is often show on a ___ shaped plot

Answer 3

funnel

Question 4

Obstacles to reaching the native state

Answer 4

1. Incorrect disulfide bond formation
2. Incorrect Xaa-Proline isomer (cis/trans)
3. Aggregation thru exposed hydrophobic surfaces during folding steps

Question 5

Advantages of ribonuclease A

Answer 5

1. Free
2. Lots available
3. Pure
4. Enzyme activity assay
5. Small and soluble
6. Helices, sheets, 4 disulphides

Question 6

Denature/renature experimental steps

Answer 6

1. Unfold ribonuclease A; 8M urea and BME
   - > Inactive enzyme
2. Dialyze ribonuclease A to remove denaturants
   - > inactive enzyme
3. Added trace amts of BME to get correct disulfides
   - > active enzyme

Question 7

Role of chaperones/chaperonins

Answer 7

1. Neither can actively fold proteins
2. Chaperones and chaperonins may be constitutively expressed (always present) or stress-regulated (so called heat shock proteins) by heat, cold, starvation, poisoning, and other forms of stress can also activate their synthesis

Question 8

Fxn of molecular chaperones

Answer 8

Prevent misfolding and aggregation, but they cannot unfold misfolded proteins.

Question 9

Prokaryotic Hsp70s are often called

Answer 9

DnaK

Question 10

What are the 2 domains of chaperone DnaK/Hsp70?

Answer 10

1. ATPase domain

2. Peptide binding domain

Question 11

2 fxns of Hsp70/chaperone DnaK

Answer 11

1. Bind to newly synthesized proteins as they come from the ribosomes to prevent them from misfolding.
2. Import of nascent proteins into organelles

Question 12

Describe Hsp90

Answer 12

1. Homodimer
2. ATPase
3. Acts together w/Hsp70 and several other chaperone proteins

Question 13

What are 4 inhibitors of Hsp90 with antitumor effect?

Answer 13

1. Geldanamycin
2. Celastrol
3. Radicicol
4. Gedunin

Question 14

Describe prefoldin

Answer 14

• 6 legged octopus
• coiled coil
• 2 top structures are beta barrel

Question 15

Fxn of chaperonins

Answer 15

Actively unfold misfolded proteins, using energy from ATP-hydrolysis

Question 16

Example of chaperonin

Answer 16

GroELGroES

Question 17

Describe the mechanism of chaperonin GroELGroES

Answer 17

• Uses ATP to refold misfolded proteins

- Rotation of ring

Question 18

Fxn of sHsp? Structure of sHsp? Example of sHsp?

Answer 18

1. In the presence of substrate proteins small heat shock proteins (sHsp) form globular oligomers with 12–42 subunits
2. Lens alpha-crystallin consists of 32 subunits, forming a globule with 190 Å outer diameter and a cavity of 100 Å.
3. The most well-known sHsp are the crystallins found in our eye lenses