Leucine zipper

The leucine zipper structure of GCN4. The leucines (yellow) and valines (magenta) form a hydrophobic zipper interaction.

Leucine zippers are a commonly occuring structural motif in protein structures, particularly in DNA-binding proteins, in which the amino acid leucine is repeated every seven amino acids within an alpha-helix structure. Additional leucines or valines may be present every 3rd or 4th position between the leucines. This sequence of amino acids creates an $\alpha$-helix with a very hydrophobic face, so that two such proteins can form what is termed a coiled-coil structure. Both homodimer and heterodimer leucine zippers occur naturally.