Structure
The main feature of the leucine zipper domain is the predominance of the common amino acid leucine at the d position of the heptad repeat. Leucine zippers were first identified by sequence alignment of certain transcription factors that identified a common pattern of leucines every seven amino acids. These leucines were later shown to form the hydrophobic core of a coiled coil.
Each half of a leucine zipper consists of a short alpha-helix with a leucine residue at every seventh position. The standard 3.6-residues-per-turn alpha-helix structure changes slightly to become a 3.5-residues-per-turn alpha-helix. Known also as the heptad repeat, one leucine comes in direct contact with another leucine on the other strand every second turn.
The bZIP family of transcription factors consists of a basic region that interacts with the major groove of a DNA molecule through hydrogen bonding, and a hydrophobic leucine zipper region that is responsible for dimerization.
Read more about this topic: Leucine Zipper
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“There is no such thing as a language, not if a language is anything like what many philosophers and linguists have supposed. There is therefore no such thing to be learned, mastered, or born with. We must give up the idea of a clearly defined shared structure which language-users acquire and then apply to cases.”
—Donald Davidson (b. 1917)