GCN4

Shown here is the leucine zipper domain of the yeast transcriptional activator GCN4.

Leucine zippers are peptide segments consisting of consecutive seven-residue repeat segments, in which the first and fourth residues are hydrophobic, with the fourth residue usually being leucine. Pairs of these peptides fold as short coiled coils. GCN4, a typical leucine zipper protein, forms a 2-stranded, parallel coiled coil in which the alpha helices wrap around each other in a left handed super coil.

The dimer of this protein is a twisted elliptical cylinder.

At the dimer interface, leucine residues make side to side interactions.

Each leucine is surrounded by 4 of the neighboring helix residues. These residues greatly contribute to the stability of the dimer.

The leucine zipper can be viewed as a twisted ladder. The sides of the ladder symbolize the helix backbone and the rungs of the ladder represent the leucine side chains.

For more information, consult:
O'Shea, Erin, et al. (1991) Science 254: 539-544.

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