Effect of pressure on the α-helix structure of tetrameric coiled-coil peptides

The effect of pressure on the α-helix structure of tetrameric coiled-coil peptides has been investigated using Fourier-transform infrared spectroscopy. To examine the influence of the hydrophobic core on pressure stability of the α-helices, the present study targeted GCN4-pLI and its variants (L9S, L9A, and L9G), which have different cavity in size. The amide II band was used to examine the stability of the hydrophobic core. From monitoring the amide I' band, it was shown commonly for all the peptides that the solvent-inaccessible α-helix decreases with increasing pressure while the solvent-accessible α-helix increases with increasing pressure. It was strongly suggested that the hydration of the helices is a significant factor for the pressure-induced folding. From further detailed analyses of pressure dependence of the amide I' band intensities, it was found that there is a positive correlation between the cavity size and the pressure-induced unfolding of the solvent inaccessible α-helix for the variants.