Check all applied 3.5 An a helical, intracellular protein, ITSME, denatures at 80 degrees Celsius. Which of thefollowing are true about ITSME?Above 80 degrees Celsius, disulfide bonds break, destabilizing the protein.Mutating 2 residues in an a helical part of ITSME to proline will likely decrease thetemperature at which ITSEME denatures.At temperatures below 80 degrees Celsius, ITSME adopts a folded structure largely dueto the hydrophobic effect.Increasing temperature provides sufficient kinetic energy to overcome the very largefree energy difference between the folded and unfolded states of ITSME.

Proteins are polymers of amino acid residues linked together via a peptide bond. The amino acid sequence of a protein dictates the protein structure and the protein structure dictates the protein function. Denaturation is the phenomenon of loss of protein function due to disruption of protein structure. ph and temperature extremes can denature the protein. Denaturation is irreversible. ITSME is a single letter code of the peptide with the amino acid sequence: H3N- Ile-Thr-Ser-Met- Glu-COO- Above 80 degrees Celsius, disulfide bonds break, destabilizing the protein. While it is true that high temperatures can break disulphide bridges and destabilise the protein structure; the given peptide lacks any cysteine residues and therefore cannot form disulphide bridges. So this statement is not applicable. Mutating 2 residues in a helical part of ITSME to proline will likely decrease the temperature at which ITSEME denatures. Ile and Thr are more likely to form beta sheets since they have bulky beta-substituted side chains that cause steric hindrance while protein folding. Ser, Met and Glu are more likely to form alpha helix as they do not have a beta-substituted side chain. If proline is substituted in place of alpha helix preferred residues, it will destabilise the helix since proline residues do not form intrastrand hydrogen bonds. Therefore the temperature of denaturation would decrease if proline is introduced in the alpha helix forming region of the peptide. So this statement is true. At temperatures below 80 degrees Celsius, ITSME adopts a folded structure largely due to the hydrophobic effect. Only 2 out of 5 amino acid residues of ITSME are hydrophobic: Ile and Met. Thr, Ser and Glu are hydrophilic residues. So hydrophobic interactions do not drive the folding of this particular protein. Increasing temperature provides sufficient kinetic energy to overcome the very large free energy difference between the folded and unfolded states of ITSME. The denaturation of a protein is not the same as the unfolding of a protein. Denaturation is an irreversible process that leads to the loss of protein function due to the loss of protein structure. Increasing the temperature disrupts the bonds that stabilise the protein structure. An unfolded protein folds into a low-energy folded state that is thermodynamically more stable than the unfolded state. So this statement is incorrect. The correct choice is the statement: Mutating 2 residues in a helical part of ITSME to proline will likely decrease the temperature at which ITSEME denatures