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Characterizing Single-Molecule Conformational Changes Under Shear Flow with Fluorescence Microscopy
Published on: January 25, 2020
Solvent-tuning the collapse and helix formation time scales of lambda(6-85)*
Charles Dumont1, Yoshitaka Matsumura, Seung Joong Kim
1Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Protein Science : a Publication of the Protein Society
|November 1, 2006
Summary
Solvent tuning can decouple protein folding processes. Lambda repressor fragment folding kinetics show distinct time scales for collapse and secondary structure formation, moving away from simple two-state folding.
Area of Science:
- Protein folding dynamics
- Biophysical chemistry
- Molecular biology
Background:
- The lambda repressor fragment (lambda(6-85)(*)) is known as a fast two-state folder.
- Engineered mutants have demonstrated near or fully downhill folding pathways.
- Solvent effects on protein stability may influence folding mechanisms.
Purpose of the Study:
- To investigate the folding thermodynamics and kinetics of lambda(6-85)(*) under stabilizing solvent conditions.
- To determine if solvent tuning alters the two-state folding behavior of lambda(6-85)(*).
Main Methods:
- Studied lambda(6-85)(*) folding in 45% aqueous ethylene glycol at -28 degrees C.
- Utilized circular dichroism (CD) at 222 nm to monitor secondary structure content.
- Employed small angle X-ray scattering (SAXS) to measure the radius of gyration.
Main Results:
- Refolding kinetics revealed decoupled time scales for collapse and secondary structure formation.
- Protein collapse occurred as a low-barrier activated process.
- Secondary structure formation approached the downhill folding limit, deviating from two-state behavior.
Conclusions:
- Two-state folding is not a robust characteristic of lambda(6-85)(*) under these conditions.
- Solvent tuning can decouple distinct folding events, altering the overall folding pathway.
- The findings provide insights into the complex nature of protein folding mechanisms.
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