Final answer:
A coiled-coil is formed from α helices with many nonpolar, hydrophobic side chains along one side, allowing for hydrophobic interactions that stabilize the structure.
Step-by-step explanation:
A coiled-coil can be formed from α helices that have many nonpolar, hydrophobic side chains along one side of the helix. This is because coiled-coils rely on the hydrophobic interaction among the side chains that protrude out from the α-helix chain to stabilize the structure. In the α-helix, the polypeptide chain adopts a right-handed coil shape, with side chains extending outward. Hydrophobic side chains on one side of the helix can interlock with hydrophobic side chains from another helix in a coiled-coil structure, allowing the two helices to wrap around each other.