Intrinsic coordination for revealing local structural changes in protein folding-unfolding

Area of Science:

• Biophysics
• Structural Biology
• Protein Dynamics

Background:

• Tracking local structural changes in unfolded proteins is challenging.
• Existing methods often lack the resolution to detail internal rearrangements during unfolding.

Purpose of the Study:

• To develop a new method for tracking internal structural changes during protein unfolding.
• To investigate the conformational dynamics of proteins under various denaturing conditions.

Main Methods:

• Utilized small-angle X-ray scattering (SAXS) for global protein morphology.
• Employed time-resolved fluorescence anisotropy (TRFA) to monitor the orientation of the protein's major axis (X) and transition dipole moment (μ).
• Developed a protein internal coordination system based on X and μ.

Main Results:

• Observed protein elongation along a reoriented major axis during unfolding induced by denaturants, acid, urea, or GuHCl.
• Quantified the relative orientation changes between the protein's major axis and transition dipole moment.
• Documented varying extents of relocation for terminal alpha helices and loop structures.

Conclusions:

• The proposed coordination method effectively tracks internal structural changes during protein unfolding.
• Protein unfolding involves significant conformational elongation and specific rearrangements of secondary structure elements.
• This approach provides new insights into the mechanisms of protein folding-unfolding pathways.