Impact of ion binding on poly-L-lysine (un)folding energy landscape and kinetics

J Phys Chem B. 2012 Jun 21;116(24):7102-12. doi: 10.1021/jp302007g. Epub 2012 Jun 6.

Abstract

We utilize T-jump UV resonance Raman spectroscopy (UVRR) to study the impact of ion binding on the equilibrium energy landscape and on (un)folding kinetics of poly-L-lysine (PLL). We observe that the relaxation rates of the folded conformations (including π-helix (bulge), pure α-helix, and turns) of PLL are slower than those of short alanine-based peptides. The PLL pure α-helix folding time is similar to that of short alanine-based peptides. We for the first time have directly observed that turn conformations are α-helix and π-helix (bulge) unfolding intermediates. ClO(4)(-) binding to the Lys side chain -NH(3)(+) groups and the peptide backbone slows the α-helix unfolding rate compared to that in pure water, but little impacts the folding rate, resulting in an increased α-helix stability. ClO(4)(-) binding significantly increases the PLL unfolding activation barrier but little impacts the folding barrier. Thus, the PLL folding coordinate(s) differs from the unfolding coordinate(s). The-π helix (bulge) unfolding and folding coordinates do not directly go through the α-helix energy well. Our results clearly demonstrate that PLL (un)folding is not a two-state process.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Ions / chemistry*
  • Kinetics
  • Perchlorates / chemistry
  • Polylysine / chemistry
  • Polylysine / metabolism*
  • Protein Folding
  • Protein Structure, Secondary
  • Sodium Compounds / chemistry
  • Spectrum Analysis, Raman
  • Water / chemistry

Substances

  • Ions
  • Perchlorates
  • Sodium Compounds
  • Water
  • Polylysine
  • sodium perchlorate