The resonance assignment, secondary structure, and dynamic properties of a stable noncoiled coil conformation of the dimerization domain from yeast transcription activation factor GCN4 (Leu zipper; LZ(GCN4)) are presented. Introduced in this paper, a new line of fully optimized spin state exchange experiments, XYEX-TROSY, applied to H-1(N), N-15 and H-1(alpha), C-13(alpha) moieties, established that in broad range of pH and buffer conditions the classical LZ(GCN4) coiled coil dimer is in a dynamic equilibrium with another distinct conformation (denoted here as x-form) and enabled complete assignment of the resonances stemming from the x-form. The LZ(GCN4) x-form is generally less structured in comparison with the classical GCN4-p1 coiled coil, but still retains a structured alpha-helical central core. The implications for folding properties and biological significance are discussed.