A coiled coil is a structural motif found in many proteins. It consists of 2-5 alpha-helices that are coiled together like the strands of a rope. Dimers and trimers are the most common ones. Coiled coils usually contain a repeated seven residue pattern called heptad repeats.

Coiled coils are held together by hydrophobic forces. When two or more alpha-helices have repeating patterns of hydrophobic amino acid side chains, the most favorable way for them to conform in the water-filled environment of the cytoplasm is to wrap the hydrophobic strands against each other sandwiched between the hydrophilic amino acids.

References

• Crick FHC. (1952) Nature, 170. 882.

• Pauling L and Corey RB. (1953) "Compound Helical Configurations of Polypeptide Chains: Structure of Proteins of the -Keratin Type", Nature, 171, 59-61.

• Crick FHC. (1953) "The Packing of a-Helices: Simple Coiled-Coils", Acta Cryst., 6, 689-697.

Protein structural motifs