a Under physiological conditions a peptide made exclusively

a)   Under physiological conditions, a peptide made exclusively of lysine (poly-lys or lysn) is disordered (it is a random coil). Under what conditions could you imagine poly-lys assuming an alpha helix?
b)   Some stretches of peptides in proteins are disordered – they don’t show any significant secondary structure. Do you think these stretches are more likely to be hydrophobic or hydrophilic? Why?
c)   Not all heat shock proteins are chaperones. Some are proteins that degrade other proteins. Why would the rate of protein degradation increase during periods when a cell is under stress, including heat stress?

Solution

1. Poly (L-lysine) exists in a random coil conformation at a low pH, alpha helix at pH of 10.6 and transforms into beta sheet when alpha helix is heated. So, pH change makes the conformational changes in the Poly lysine.

2. The inner core of the secondary structure of the protein is hydrophobic. The disordered streteches of peptides is non-polar in nature.