Synthesis and properties of the peptide corresponding to the mutant form of the leucine zipper of the transcriptional activator GCN4 from yeast.

A 33 membered polypeptide corresponding to the leucine zipper region of the yeast transcriptional activator GCN4 was synthesized by solid phase chemical synthesis and characterized. Asparagine in the hydrophobic core of the molecule is replaced by valine in the synthetic variant. The correctness of amino acid sequence of the preparation is corroborated by direct sequencing. High-speed equilibrium ultracentrifugation, ultraviolet circular dichroism spectroscopy and scanning microcalorimetry have been employed to demonstrate that in solution the peptide forms a highly stable triple-stranded alpha-helical coiled coil. The stability of the mutant form is 40 degrees C higher than the dimeric form of natural peptide under similar conditions. It was proposed that location of some polar groups in the 'a' and 'd' positions of natural two-stranded coiled coils may be regarded as protection against alternative triple- and multistranded conformations.