#Question id: 886
#Unit 1. Molecules and their Interaction Relevant to Biology
An experiment of Anfinsen on ribonuclease A (RNase A) showed that proteins can be denatured reversibly by 2-mercaptoethanol and 8 M urea. The protein must therefore renature spontaneously;
a) Remove mercaptoethanol and then removal of the urea
b) Removal of the mercaptoethanol allows the protein to re-form disulfide bonds in the presence of oxygen and then removal of the urea
c) Removal of the denaturant (urea) and reductant (mercaptoethanol) allows the protein to renature and re-form disulfide bonds in the absence of oxygen
d) Adding a small amount of mercaptoethanol to the scrambled protein in the absence of O2 catalyzes its conversion to the active enzyme
Which one of the following steps will leads to regaining of the full activity of ribonuclease A (RNase A)
#Question id: 887
#Unit 1. Molecules and their Interaction Relevant to Biology
Polypeptides fold rapidly by a stepwise process, how does the polypeptide chain arrive at its native conformation?
#Question id: 888
#Unit 1. Molecules and their Interaction Relevant to Biology
Which one of the following statements about the protein folding is incorrect?
#Question id: 889
#Unit 1. Molecules and their Interaction Relevant to Biology
The cis and trans GroEL rings undergo conformational changes in a reciprocating fashion, with events in one ring influencing events in the other ring. The entire GroEL/ES chaperonin complex functions as follows;
a) One GroEL ring that has bound 7 ATP also binds an improperly folded substrate protein, which associates with hydrophobic patches that line the inner wall of the GroEL chamber
b) The GroES cap then binds to the GroEL ring like a lid on a pot, inducing a conformational change in the resulting cis ring
c) Within ~10 s the cis ring catalyzes the hydrolysis of its 7 bound ATPs and releases the resulting Pi , which weakens the interactions binding GroES to GroEL
d) A second molecule of improperly folded substrate protein binds to the cis ring, followed by 7 ATP
e) The binding of substrate protein and ATP to the cis ring conformationally induces the trans ring to release its bound GroES, 7 ADP, and the presumably now better-folded substrate protein
Which of the following is incorrect functions of GroEL/ES chaperonin complex?
#Question id: 890
#Unit 1. Molecules and their Interaction Relevant to Biology
Some of the misfolded protein or defective Protein causes disease as follows;
| Disease | Defective Protein |
| A) Parkinson's disease | i) Amyloid-β protein |
| B) Alzheimer's disease | ii) Superoxide dismutase |
| C) Huntington's disease | iii) Lysozyme |
| D) Lysozyme amyloidosis | iv) α-Synuclein |
| E) Amyotrophic lateral sclerosis | v) polyglutamate expansion |
#Question id: 891
#Unit 1. Molecules and their Interaction Relevant to Biology
The folding pathways of some proteins require two enzymes that catalyze isomerization reactions such as,
a) Peptide prolyl isomerase (PPI) catalyzes the elimination of folding intermediates with inappropriate disulfide cross-links
b) Protein disulfide isomerase (PDI) enzyme that catalyzes the interchange, or shuffling, of disulfide bonds until the bonds of the native conformation are formed
c) Peptide prolyl cis-trans isomerase (PPI) catalyzes the interconversion of the cis and trans isomers of Proline residue peptide bonds
d) Peptide prolyl isomerase (PPI) can be a fast step in the folding of proteins that contain some Pro peptide bonds in the cis conformation
Which of the following combinations is correct about protein folding pathways?