Lecture 14 Flashcards
Where are Hydrophobic side chains most likely to be found?
In the interior of a globular proteins
Where are Hydrophilic side chains most likely to be found?
In the surface of a globular protein
What is the Hydrophobic core of proteins generally enriched with?
Regular secondary structures
Where do Irregular protein structures usually exist and why?
On the surface of proteins because they don’t satisfy the H-bond potential and need something polar to interact with those groups
What is the driving force for which soluble globular proteins adopt and maintain their 3º structure?
The hydrophobic effect
What does the Shape of Globular proteins depend on?
The relative positions of hydrophobic amino acids in the proteins 1º structure
What helps to fine tune and stabilize 2º and 3º structures?
- Hydrogen bonding between polar side chains
- Ion pairs (salt bridges)
- Disulfide bonds/bridges
What are Ion Pairs (Salt Bridges)?
Electrostatic interactions between closely-positioned formal charged groups on amino acids
What are the Positive charges in amino acids?
- N-terminus
- Lys
- Arg
- (His)
What are the Negative charges in amino acids?
- C-terminus
- Asp
- Glu
- (Tyr)
- (Cys)
What are Disulfide Bonds/Bridges?
Covalent bonds between closely-positioned cysteines that occurs in an oxidizing environment
What do Disulfide bonds form stabilizing crosslinks for?
Extracellular proteins in the lumen
Why don’t Cytosolic proteins contain disulfides?
Because the cytosol is a reducing environment and we would cystines in the environment not cysteines which can form disulfides
What interactions are the most important for Soluble Globular proteins?
Hydrophobic interactions
What is a Domain?
A polypeptide segment that has folded into a single structural unit with a hydrophobic core ex. The different segments of a sweater (arms, trunk)
What is a Motif?
A short region of a polypeptide with a recognizable 3D shape ex. The different types of stitching
What is an example of a motif?
Zinc fingers
What are Zinc Fingers?
A structural motif including a prosthetic group
What is a Prosthetic group?
A non-peptide component that is permanently incorporated into a protein
What is an example of a prosthetic group in blood?
Heme
What are Globular proteins stabilized by?
Weak noncovalent forces
What can Globular proteins be unfolded by?
- Heat
- Changes in pH
- Salt
- Detergents
Which stabilizing forces can Heat affect?
H-bonds and Hydrophobic interactions
Which stabilizing forces can changes in pH affect?
Salt bridges/H bonds
