X-Ray Structure of the GCN4 Leucine Zipper, a Two-Stranded, Parallel Coiled Coil

Abstract

The x-ray crystal structure of a peptide corresponding to the leucine zipper of the yeast transcriptional activator GCN4 has been determined at 1.8 angstrom resolution. The peptide forms a parallel, two-stranded coiled coil of alpha helices packed as in the "knobs-into-holes" model proposed by Crick in 1953. Contacts between the helices include ion pairs and an extensive hydrophobic interface that contains a distinctive hydrogen bond. The conserved leucines, like the residues in the alternate hydrophobic repeat, make side-to-side interactions (as in a handshake) in every other layer of the dimer interface. The crystal structure of the GCN4 leucine zipper suggests a key role for the leucine repeat, but also shows how other features of the coiled coil contribute to dimer formation.

Effect of Bcr sequences on the cellular function of the Bcr-Abl oncoprotein

“…If true, we should be able to exchange the Bcr coiled-coil with another oligomerization domain and retain activation. We therefore replaced the N-terminal 63 amino acids of Bcr/1-509-Abl with a coiled-coil from a completely unrelated protein: the leucine zipper from the yeast transcription factor GCN4 (O'Shea et al, 1991). The C-terminal 34 amino acids of GCN4 which contain the leucine zipper domain were ®tted with a consensus eukaryotic translation initiation sequence and then fused in frame with the Bcr-Abl coding region (Figure 1, ZIP-Bcr/64-509-Abl).…”

Probing the roles of residues at the e and g positions of the GCN4 leucine zipper by combinatorial mutagenesis

“…Intersubunit salt bridges at three such pairs of sites are observed in the crystal structure of the GCN4 leucine zipper (O'Shea et al, 1991;Ellenberger et al, 1992). One of the goals of this work was to assess the importance of these kinds of salt bridges in stabilizing the leucine zipper.…”

“…The most extensively characterized leucine zipper is from the yeast transcriptional activator GCN4. Detailed structures have been determined by X-ray crystallography for both the leucine zipper domain (Kinemage 1; O'Shea et al, 1991) and the basic-region leucine zipper motif bound to DNA (Ellenberger et al, 1992). Structural properties of the GCN4 leucine zipper have also been studied in solution by two-dimensional NMR spectroscopy (Oas et al, 1990), amide proton exchange (Goodman & Kim, 1991), and biochemically using synthetic leucine zipper peptides (O'Shea et al, 1989a).…”

“…Figure 1 shows a cartoon representation of the GCN4 leucine zipper. The dimer consists of two right-handed a-helical monomers in a parallel coiled coil with local twofold symmetry throughout most of its length (O'Shea et al, 1991). The dimer interface of the leucine zipper is formed largely by contacts involving side chains designated as the a, d, e, and g positions of the heptad repeat.…”

Bacterial expression and characterization of the CREB bZip module: Circular dichroism and 2D 1H‐NMR studies

“…Structural studies of synthetic peptides corresponding to the leucine zipper motif of GCN4 demonstrated that this domain assumes a coiled-coil 1461 structure of parallel helices (O'Shea et al, 1989a,b;Oas et al, 1990). The a-helical structure and parallel coiledcoil arrangement of this domain have been corroborated by two-dimensional (2D) 'H-NMR (Oas et al, 1990) and X-ray crystallographic data (O'Shea et al, 1991). The DNA binding domain of leucine zipper proteins is predominantly a basic region of approximately 30 amino acid residues located upstream of the leucine zipper motif.…”