Final answer:
Coiled-coils in proteins are stabilized predominantly by hydrophobic interactions that occur between the hydrophobic side chains of nonpolar amino acids.
Step-by-step explanation:
The stable wrapping of one helix around another in coiled-coils is typically driven by hydrophobic interactions.
In the formation of protein tertiary structures, hydrophobic interactions play a vital role. The hydrophobic R groups of nonpolar amino acids locate to the interior of the protein, leading to the coiled-coil conformation. These interactions are a result of the hydrophobic side chains of amino acids avoiding contact with water and, as such, fold towards the inside of the protein structure. This self-assembly process is crucial for the proper folding and stability of the protein's three-dimensional shape, allowing for specific functional conformations. It is these interactions that enable the alpha helices to wrap around each other, creating the stable structure.
Coiled-coils are formed when two or three α helices wrap around each other. The stable wrapping of one helix around another is mainly driven by hydrophobic interactions.
Hydrophobic interactions occur between the nonpolar amino acid side chains that face inwards towards each other, away from the surrounding water. These hydrophobic interactions are a result of van der Waals forces, which are weak attractive forces between nonpolar molecules.
In contrast, hydrophilic interactions involve the attraction between polar or charged molecules with water. Ionic bonds, which result from the attraction between oppositely charged ions, are one type of hydrophilic interaction. However, the wrapping of α helices in coiled-coils is primarily driven by hydrophobic interactions.