Lecture 13-14

Question 1

Tertiary folding is usually stabilized by?

Answer 1

non colvalent interactions
-Hydrophobic interactions
-H-bonds
-Ionic interactions
-Van Der Waals forces

Question 2

Denaturing can be caused by

Answer 2

-Raising temp
-Extreme PH
-Detergents that disrupt hydrophobic regions

Question 3

What are reducing agents

Answer 3

Agents like B-ME reduce disulphide bonds and as they are reduced, the agent is oxidized and forms disulphide-bonded dimers

Question 4

Denaturants

Answer 4

Disrupt weak non-covalent interactions that stabilize folded proteins
(8M urea)

Question 4

Describe Chris Anfinsens experiment

Answer 4

-Ribonuclease protein was denatured in the presence of urea and BME, which disrupted the noncovalent interactions and the four disulfide bonds, resulting in loss of enzyme activity
-If the urea and BME were removed at the same time by dialysis, the correct disulfide bonds were formed, and the enzyme regained full activity
-if the BME was removed first, and then the urea, the protein incorrectly refolded and remained inactive due to incorrect disulfide bond formation.

Question 5

What are the 3 proposed models of protein folding pathways

Answer 5

-Hydrophobic collapse model
-Framework model
-Nucleation Model

Question 6

Describe the GroEL-GroEs folding cycle

Answer 6

1. GroES and ATP bind to the GroEL ring, trapping an unfolded protein within the folding chamber
2. Conformational change releases GroES, and folded protein exits the lower chamber
3. ATP hydrolysis causes conformational change in upper chamber and resets the lower chamber for another round
4. A new unfolded protein enters the lower chamber, and the cycle continues

Question 7

Fibrous vs Globular Proteins

Answer 7

Fibrous: Highly elongated molecules whose shapes are dominated by a single structure

Globular: Have compact roughly spherical shapes (RNase A)