Chapter 26, Problem 26.66P

Interpretation Introduction

Interpretation:

Some polypeptides can dimerize to form a coiled coil, a structural motif where one $\text{α-helix}$ wraps around another (shown below).

Typically the primary structure of each polypeptide has a seven–amino acid repeating pattern, in which the first and third amino acids are hydrophobic. As a result, a stripe of hydrophobic side chains extends down the length of each α-helix. It is to be explained how this stabilizes the coiled coil in an aqueous environment.

Concept introduction:

An aqueous environment is hydrophilic. The hydrophobic amino acid is hidden from the aqueous environment and hydrophilic (water-loving) amino acids are exposed to the aqueous environment. In short hydrophilic amino acids are strongly attracted by the water molecules and hydrophobic amino acids are insoluble in water and repelled by the water molecules.