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A leucine zipper, aka leucine scissors[1], is a super-secondary structural motif found in proteins that creates adhesion forces in parallel alpha helices.[2] It is a common dimerization domain found in some proteins involved in regulating gene expression. Leucine zippers are found in both eukaryotic and prokaryotic regulatory proteins but are mainly a feature of Eukaryotes. An amphipathic alpha helix is formed with a hydrophobic region at one side having basic aminoacids. This hydrophobic region provides an area for attachment of 2 polypeptides.
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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 which 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 heptat repeat, one leucine comes in direct contact with another leucine on the other strand every second turn.
The bZip family of transcription factors consist of a basic region which interacts with the major groove of a DNA molecule through hydrogen bonding, and a hydrophobic leucine zipper region which is responsible for dimerization.
Biology
Leucine zipper regulatory proteins include c-fos and c-jun (the AP1 transcription factor), important regulators of normal development. If they are overproduced or mutated in a vital area, they may generate cancer. These proteins interact with the DNA as dimers (homo- or hetero-) and are also called basic zipper proteins (bZips).
References
- ^ David M. Glick, ed (1997). "Leucine scissors". Glossary of Biochemistry and Molecular Biology (Revised ed.). London: Portland Press.
- ^ Landschulz WH, Johnson PF, McKnight SL (1988-06-24). "The leucine zipper: a hypothetical structure common to a new class of DNA-binding proteins". Science 240 (4860): 1759-1764. PMID 3289117.
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