Question 5 of 16
Some proteins are rich in disulfide bonds, and their mechanical properties such as tensile strength, viscosity, hardness, etc., correlate with the degree of disulfide bonding.
Glutenin, a wheat protein rich in disulfide bonds, imparts the cohesive and elastic character of dough made from wheat flour. Similarly, the hard, tough nature of tortoise shell results from the extensive disulfide bonding in its $\alpha$-keratin.
What is the molecular basis for the correlation between disulfide-bond content and mechanical properties of the protein?
O Disulfide bonds act as intramolecular cross-links that stabilize proteins.
O Disulfide bonds give rigidity to a protein and prevent any conformational changes.
O Proteins containing disulfide bonds participate in more protein-protein interactions.
O Proteins containing disulfide bonds have a longer half-life in the cytosol.
Most globular proteins denature and lose their activity when briefly heated to 65 $^\circ$C. However, globular proteins that contain multiple disulfide bonds often require longer heat exposure at higher temperatures to denature them. One such protein is bovine pancreatic trypsin inhibitor (BPTI). BPTI has 58 amino acid residues in a single peptide chain and contains three disulfide bonds. After cooling a solution of heat denatured BPTI, the protein regains its activity.
What is the molecular basis for this property of BPTI?
O Disulfide bonds lower the optimal temperature of the reaction BPTI participates in.
O Disulfide bonds protect BPTI from peptide bond hydrolysis during heating.
O Disulfide bonds prevent the complete unfolding of BPTI at high temperatures.
O Disulfide bonds make BPTI more rigid at high temperatures than low temperatures.