What are the regular secondary structures that polypeptides can fold into?
α helix, β pleated sheets, β strands, β turns, Ω loop
Describe the α helix
A rod-like structure; a tightly coiled backbone forms the inner part of the rod and the side chains extend outwards. It is stabilised by hydrogen bonds between the NH and CO groups of the main chain.
What are the two directions that β strands can run in β sheets?
Parallel and anti parallel
A term describing a chemical compound that possesses hydrophilic and lipophillic properties.
What did Anfinsen's experiments reveal?
That the information needed to specify catalytically active structure is contained in the amino acid sequence
What are the steps of denaturation in Anfinsen's experiment?
On ribonuclease: - non-covalent bonds are disrupted using urea/guanidinium - disulphides bonds are reversibility cleaved using β-mercaptoethanol - the causes denaturation
When denaturing a protein there is a sharp transition between the native and denatured state. What does this suggest?
These are the only two states present and the unfolding is an 'all or nothing' process
What kind of assistance can increase the rate of protein folding?
Chaperone assisted folding
How does chaperone assisted folding increase the rate of protein folding?
It works by sheilding hydrophobic surfaces to prevent aggregation, and by isolating chains to prevent interferance from other intermediates.
What diseases are associated with improperly folded proteins?
Alzheimer's, Parkinson's, Huntington's, and prion disease
What are examples of transmissible spongiform encephalopathies?
Bovine spongiform encephalopathy, creutzfeldt-Jacob disease, and scrapie
How are transmissible spongiform encephalopathies transmitted?
Prions. Agents that are similar in size to viruses, but consist entirely of protein
What are prions composed of?
The protein PrP
What happens when a prion is mutated by being acquired?
The PrP proteins change from PrPc to PrPsc. This causes the alpha helical conformations to change to beta strands.