Secondary, tertiary, and quaternary structure II

What is an example of a conformational disease?

Alzheimers disease

How does Alzheimers disease occur?

There is a structural change in the alpha helix of a human amyloid peptide that normally forms. This causes several peptides to stick together and turns into a repeating beta sheet (end up with a beta-amyloid fibril).

What happens in mad cow disease?

There are proteins called prions that can be misfolded (have more beta sheet) and then they self propagate and catalyze creation of misfolded proteins that aggregate and cause this disease

What is the native state?

It is the functional state of a protein

What is a denatured state?

It is a non-functional state of a protein

What is the native state stabilized by?

1. Hydrophobic effect (entropy of water)

2. Enthalpic interactions (H bonds, VDW)

What is the denatured state stabilized by?

The peptide chain having a high entropy

Can a denatured proteins become a precipitated protein? Is this reversible or irreversible?

Yes and it is irreversible

What are four factors that can denature proteins?

1. Heat

2. pH extremes

3. Chemicals

4. Mutations

What is quaternary structure?

It is when protein complexes contain protein subunits (individual peptide chains). They can be dimer, trimer, etc and homo or hetero.

What is hemoglobin?

It is a heterotetramer (has quaternary structure)

What are the three benefits of quaternary structure?

1. Don’t need to synthesize/fold one huge chain

2. Subunits can be recycled for new purposes

3. Potential for complex interactions between subunits