Fast Events in Protein Folding: Helix Melting and Formation in a Small Peptide

Authors:
Publisher website
Google Scholar
Abstract
The helix is a common secondary structural motif found in proteins, and the mechanism of helix−coil interconversion is key to understanding the protein-folding problem. We report the observation of the fast kinetics (nanosecond to millisecond) of helix melting in a small 21-residue alanine-based peptide. The unfolding reaction is initiated using a laser-induced temperature jump and probed using time-resolved infrared spectroscopy. The model peptide exhibits fast unfolding kinetics with a time constant of 160 ± 60 ns at 28 °C in response to a laser-induced temperature jump of 18 °C which is completed within 20 ns. Using the unfolding time and the measured helix−coil equilibrium constant of the model peptide, a folding rate constant of approximately 6 × 107 s-1 (t1/2 = 16 ns) can be inferred for the helix formation reaction at 28 °C. These results demonstrate that secondary structure formation is fast enough to be a key event at early times in the protein-folding process and that helices are capable of forming before long range tertiary contacts are made.

This publication has 11 references indexed in Scilit: