Protein Folding Flashcards
What is the Levinthal Paradox
For 100 residues protein. Assuming 10 confirmations for each residue 10^100.
Sampled at rate of 10^13 per second (rate of rotation about a single bond)
10^80 years to sample all confirmations.
How was the BPTI folding pathway studied?
Lower temp to make fold more slowly - glucose, viscous solution - stretched folding to ~10S.
Took aliquots
Used MS analysis to look at free & disulphide bonded cysteines.
What have been the results of unfolding experiments?
chymotrypsin inhibitor - sheets fall apart & last thing left = helix.
Barnase - 4 stranded B-sheet flanked by 2 alpha helices - same observation as above.
Same for engrailed homeodomain protein.
Which protons exchange in H/D exchange?
protons attached to backbone amide group (those involved in H bonds and hence secondary structure are protected).
Outline temperature jump.
Protein (unfolded) and hydrogen peroxide at low temp..
Laser pulse –> T jump & initiates folding.
2nd laser pulse (different wavelength) - forms OH which attacks EXPOSED side chains.
Mass spec to determine protein mass.
Define a molten globule state.
Secondary structural elements with substantial mobility,
Hydrophobic side chains still not locked together.
Core still contains water.
What are the global features of chaperonins?
~60 kDa monomers form DOUBLE RING oligomers.
Each ring encloses a cavity in which protein folding takes place.
Open, substrate receptive confo.
Closed conformation (S isolated)
Transition induced upon ATP binding –> complex intra & inter ring allosteric signals.
How is it believed that Artic flounder antifreeze prevents ice formation?
Give one feature of the protein.
Network of H-bonded water molecules extends into soln with surrounding water molecules.
Low free energy of folding (protein not stable above 16C)
