#Question id: 909
#Unit 1. Molecules and their Interaction Relevant to Biology
Most proteins denature at both high and low pH. At high pH, the ionization of internal tyrosines is thought to be the main destabilizing influence, whereas at low pH, the protonation of buried histidines. A titration curve for the unfolding of the enzyme ribonuclease is shown in Figure. Given the relation between the titration curves for protein unfolding and histidine protonation, which of the following conclusion can be drawn correctly?
A. The sharp transition in graph indicates a highly cooperative process; when the protein starts to unfold, it completes the process rapidly
B. The sharp transition in graph indicates a highly noncooperative process
C. Several buried histidines can ionize when the chain starts to unfold, so that when one goes, they all go together due to cooperative behaviour of protein folding
D. Buried histidine (pK of 4 in this example) becomes accessible to solvent, its pK will shift toward its normal value of 6, significantly steepening its titration curve.
#Question id: 910
#Unit 1. Molecules and their Interaction Relevant to Biology
Experiments on denaturation and renaturation after the reduction and reoxidation of the —S—S— bonds in the enzyme ribonuclease (RNase) have shown that:
#Question id: 911
#Unit 1. Molecules and their Interaction Relevant to Biology
The correct order for molecular chaperone–mediated protein folding is:
I – exchange of ATP for ADP on chaperone
II – chaperone undergoes conformational change, which affects protein folding
III – chaperone binds to exposed hydrophobic residues on unfolded protein
IV – folded protein is released
#Question id: 912
#Unit 1. Molecules and their Interaction Relevant to Biology
Which of the following is correct about the native state of a protein
a. is unaffected by changes in temperature and pH.
b. corresponds to the highest Gibbs free energy state.
c. is determined by its primary amino acid sequence.
d. corresponds to the lowest entropic state.
#Question id: 913
#Unit 1. Molecules and their Interaction Relevant to Biology
The appropriate folding of a newly translated product is essential, and continual misfolding often leads to disease, especially in vertebrates. This misfolding, particularly in the situation of prion diseases, may be due to
#Question id: 914
#Unit 1. Molecules and their Interaction Relevant to Biology
Lipoprotein lipase acts in: