Exposing the Nucleation Site in α-Helix Folding: A Joint Experimental and Simulation Study

Area of Science:

• Protein folding dynamics
• Biophysical chemistry
• Molecular dynamics simulations

Background:

• Alpha-helix formation is fundamental to protein folding, involving specific hydrogen bonds.
• The precise location of the initial helical nucleation event remains elusive.
• The asymmetric nature of alpha-helices suggests a preferred nucleation site.

Purpose of the Study:

• To identify the specific location of the productive nucleation event in alpha-helix formation.
• To investigate the role of nucleation site in the overall folding pathway.
• To evaluate the impact of cross-linking on protein conformation.

Main Methods:

• Peptide cross-linking experiments
• Laser-induced temperature-jump infrared spectroscopy
• All-atom molecular dynamics simulations

Main Results:

• Experimental and simulation data support N-terminal nucleation for alpha-helix folding.
• The productive nucleus forms at the N-terminus and propagates C-terminally.
• Cross-linker incorporation can induce alternative folded conformations.

Conclusions:

• The productive nucleation site for alpha-helix formation is located at the N-terminus.
• This N-terminal nucleus drives the propagation of the helix towards the C-terminus.
• Cross-linking strategies require careful consideration and validation through simulations.