Leucine zipper

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Associate Editor(s)-in-Chief: Henry A. Hoff

File:Coiledcoil-wheelcartoon.gif
"Overhead view", or helical wheel diagram, of a leucine zipper, where d represent amino acid leucine , arranged with other amino acids on two parallel alpha helices.

A leucine zipper, aka leucine scissors[1], is a super secondary structural motif found in proteins that creates adhesion forces in parallel alpha helices. It is a common dimerization domain found in some proteins involved in regulating gene expression.

Structure

File:Leucine zipper.png
Leucine Zipper (blue) bound to DNA. The leucine residues that represent the 'teeth' of the zipper are colored red

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 leucine zipper region which is responsible for dimerization.

bZIP DNA binding domains

Leucine zippers are a dimerization motif of the BZIP domain (bZIP) (Basic-region leucine zipper) class of eukaryotic transcription factors.[2] The bZIP domain is 60 to 80 amino acids in length with a highly conserved DNA binding basic region and a more diversified leucine zipper dimerization region.[3] The localization of the leucines are critical for the DNA binding to the proteins. Leucine zippers are present in both eukaryotic and prokaryotic regulatory proteins, but are mainly a feature of eukaryotes.

They can also be annotated simply as ZIPs, and ZIP-like motifs have been found in proteins other than transcription factors and are thought to be one of the general protein modules for protein–protein interactions.[4]

The bZIP interacts with DNA via basic, amine residues (see basic amino acids in (provided table (sort by pH)) of certain amino acids in the "basic" domain, such as lysines and arginines. These basic residues interact in the major groove of the DNA, forming sequence-specific interactions. The mechanism of transcriptional regulation by bZIP proteins has been studied in detail. Most bZIP proteins show high binding affinity for the ACGT motifs, which include CACGTG (G box), GACGTC (C box), TACGTA (A box), AACGTT (T box), and a GCN4 motif, namely TGA(G/C)TCA.[5][3][6] The bZIP heterodimers exist in a variety of eukaryotes and are more common in organisms with higher evolution complexity.[7] Heterodimeric bZIP proteins differ from homodimeric bZIP and from each other in protein-protein interaction affinity.[8] These heterodimers exhibit complex DNA binding specificity. When combined with a different partner, most of the bZIP pairs bind to DNA sequences that each individual partner prefers. In some cases, dimerization of different bZIP partners can change the DNA sequence that the pair targets in a manner that could not have been predicted based on the preferences of each partner alone. This suggests that, as heterodimers, bZIP transcription factors are able to change their preferences for which location they target in the DNA. The ability of bZIP domain forming dimers with different partners greatly expands the locations on the genome to which bZIP transcription factors can bind and from which they can regulate gene expression.[8]

A small number of bZIP factors such as OsOBF1 can also recognize palindromic sequences.[9] However, the others, including LIP19, OsZIP-2a, and OsZIP-2b, do not bind to DNA sequences. Instead, these bZIP proteins form heterodimers with other bZIPs to regulate transcriptional activities.[9][10]

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).

See also

References

  1. David M. Glick, ed. (1997). "Leucine scissors". Glossary of Biochemistry and Molecular Biology (Revised ed.). London: Portland Press.
  2. Vinson CR, Sigler PB, McKnight SL (November 1989). "Scissors-grip model for DNA recognition by a family of leucine zipper proteins". Science. 246 (4932): 911–6. Bibcode:1989Sci...246..911V. doi:10.1126/science.2683088. PMID 2683088.
  3. 3.0 3.1 E ZG, Zhang YP, Zhou JH, Wang L (April 2014). "Mini review roles of the bZIP gene family in rice". Genetics and Molecular Research. 13 (2): 3025–36. doi:10.4238/2014.April.16.11. PMID 24782137.
  4. Hakoshima, T. (2005). "Leucine Zippers". Encyclopedia of Life Sciences. doi:10.1038/npg.els.0005049. ISBN 0470016175.
  5. Landschulz WH, Johnson PF, McKnight SL (June 1988). "The leucine zipper: a hypothetical structure common to a new class of DNA binding proteins". Science. 240 (4860): 1759–64. Bibcode:1988Sci...240.1759L. doi:10.1126/science.3289117. PMID 3289117.
  6. Nijhawan A, Jain M, Tyagi AK, Khurana JP (February 2008). "Genomic survey and gene expression analysis of the basic leucine zipper transcription factor family in rice". Plant Physiology. 146 (2): 333–50. doi:10.1104/pp.107.112821. PMC 2245831. PMID 18065552.
  7. Reinke AW, Baek J, Ashenberg O, Keating AE (May 2013). "Networks of bZIP protein-protein interactions diversified over a billion years of evolution". Science. 340 (6133): 730–4. Bibcode:2013Sci...340..730R. doi:10.1126/science.1233465. PMC 4115154. PMID 23661758.
  8. 8.0 8.1 Rodríguez-Martínez JA, Reinke AW, Bhimsaria D, Keating AE, Ansari AZ (February 2017). "Combinatorial bZIP dimers display complex DNA-binding specificity landscapes". eLife. 6: e19272. doi:10.7554/eLife.19272. PMC 5349851. PMID 28186491.
  9. 9.0 9.1 Shimizu H, Sato K, Berberich T, Miyazaki A, Ozaki R, Imai R, Kusano T (October 2005). "LIP19, a basic region leucine zipper protein, is a Fos-like molecular switch in the cold signaling of rice plants". Plant & Cell Physiology. 46 (10): 1623–34. doi:10.1093/pcp/pci178. PMID 16051676.
  10. Nantel A, Quatrano RS (December 1996). "Characterization of three rice basic/leucine zipper factors, including two inhibitors of EmBP-1 DNA binding activity". The Journal of Biological Chemistry. 271 (49): 31296–305. doi:10.1074/jbc.271.49.31296. PMID 8940135.
  • Landschulz WH, Johnson PF, McKnight SL. (1988) The leucine zipper: a hypothetical structure common to a new class of DNA-binding proteins. Science 240:1759-1764. PubMed abstract

External links

de:Leucin-Zipper