Define Protein Folding
The process by which a protein obtains its natural 3D state
The process by which a polypeptide chain is created from mRNA
The process by which DNA sequences are converted into an mRNA chain
Which structure of a protein shows biological activity?
Which of the following occurs to ALL proteins?
Which of the following are covalent modifications of the polypeptide chain?
Formation of disulphide bonds
Van Der Waals interactions
Folding corresponds to a hierarchy of protein structure
Put the following in Order
B - Nucleation
C - Secondary Structure
D - Domain
E - Active Oligomer
F - Inactive Oligomer
G - Supersecondary Structure
H - Folded Monomer
What is meant by the 'Thermodynamic Hypothesis of Protein Folding'
That proteins fold into different structures based on the energy available to them in the medium
That the information for correct protein folding is found within the sequence itself
That the protein will always fold into the lowest possible energy state
The Kinetic Hypothysis suggests that there is a specific folding pathway for each protein- protein folding is not random
Describe the features of the RNAase Refolding experiment?
RNAase is denatured with urea
RNAase is denatured with detergent
And an oxidising agent to remove the disulphide bridges
And a reducing agent to remove the disulphide bridges
Once the denaturing agents were removed and it was re-oxdised
Once the denaturing agents were removed and it was re-reduced
Protein fully reformed itself and worked
How do we know the RNAase really was denatured during the experiment?
If the protein was allowed to reform before the reducing agents were removed, the sequence showed non native sulphides and didn't work
We don't know- we can never really KNOW anything
If the protein was allowed to reform before the reducing agents were removed, the sequence didn't work
Which of the following are conditions for In Vitro Refolding (Like in the RNAase experiment)?
Structure must be amenable to environmental changes
Free energy path must be relatively smooth
Must contain covalent bonds
Must have slow transitions
Structure must have unique free energy
What type of amino acid is being shown ere?
Trans formations are less stable due to their steric hindrance
Proline is added to an amino acid chain exclusively in what form?
The other form occurs 10-40% of the time, and must be altered post addition
Which of the following proteins converts cis isomers to their trans form?
Peptidyl Propyl Isomerases
Peptidyl Glucyl Isomerases
Peptidyl Lipyl Isomerases
In the Cis form, the clash of functional groups around the alpha carbon is much greater due to steric hindrance
What type of bond is being shown here?
Van Der Waals
The previous amino acid to proline experiences steric hindrance in either proline conformation
Cis proline has _ energy than/to trans proline
The two cystine molecules that bind together are known as what?
Proteins with di-sulphide bonds are most likely to be found where?
In low/high pH
In low/high salt concentrations
Phosphorylation occurs on which residues?
Pro-sequences are found at the C-terminus
The Pro-sequence is also known as
A chaperone sequence
A ligation sequence
A glycosylation sequence
Which proteins will have a pro-sequence?
The protein with a pro-sequence will auto-cleave it before folding correctly
What is co-operativity in protein folding?
Where one area of the protein that has already folded provides a nucleation site for another domain to fold
The pre-formed proteins will be used as a template to fold more of that species
Where chaperone proteins assist in protein folding
What does the Hydrophobic Zipper Model suggest?
That hydrophobic amino acids in close proximity are more likely to interact
That hydrophillic amino acids in close proximity are more likely to interact
Constraining the chain and making other residues more likely to interact, which further constrains the chain, etc.