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: 861

#Part-B Specialized Branches in Biotechnology

Alexander Varshavsky discovered, the half-lives of many cytoplasmic proteins vary with the identities of their N-terminal residues via the so-called N-end rule:-

#Question id: 863

#Part-B Specialized Branches in Biotechnology

Ubiquitinated proteins are proteolytically degraded in an ATP-dependent process mediated by a large (∼2500 kD, 26S) multiprotein complex named the 26S proteasome;

#Question id: 865

#Part-B Specialized Branches in Biotechnology

In autophagy, the endoplasmic reticulum (ER) first gives rise to a cup-shaped, membranous cisterna called the______

#Question id: 869

#Part-B Specialized Branches in Biotechnology

Which statements are correct regarding protein folding

A. Many molecular chaperones were first described as heat shock proteins (Hsp) because Their rate of synthesis is increased at elevated temperatures

B. The renaturation of a denatured protein in vitro may not entirely mimic the folding of a protein in vivo.

C. Molecular chaperones are essential proteins that bind to only partially folded polypeptide chains.

D. Molecular chaperones function to lift folding polypeptides out of the false minima in their folding funnel.

#Question id: 872

#Part-B Specialized Branches in Biotechnology

Which of the following statements is not true about HSP 70 family.

A. They have a molecular weight near 70,000 and are abundant in cells stressed by elevated temperature.

B. Bind to regions of unfolded polypeptides that are rich in hydrophilic residues

C. Hsp70 proteins not  block the folding of certain proteins that must remain unfolded untill they have been translocated across a membrane.

D.) It releases polypeptides in a cycle that uses energy from ATP hydrolysis.

#Question id: 875

#Part-B Specialized Branches in Biotechnology

Why positive phi angles less common than negative Phi angles in proteins contain L amino acid?