Refolding of the immunoglobulin light chain

Area of Science:

• Biochemistry
• Protein Folding
• Immunology

Background:

• Bence Jones proteins are immunoglobulin light chains implicated in multiple myeloma.
• Understanding their refolding kinetics is crucial for comprehending protein misfolding diseases.

Purpose of the Study:

• To investigate the refolding kinetics of type lambda Bence Jones proteins and their variable (VL) and constant (CL) domains.
• To elucidate the interplay between VL and CL domain refolding within the intact Bence Jones protein.

Main Methods:

• Circular dichroism (CD) spectrophotometry.
• Ultraviolet (UV) absorption spectrophotometry.
• Fluorescence spectrophotometry.
• Refolding studies from 4 M GuHCl.

Main Results:

• Refolding kinetics exhibited at least three phases: undetectable fast, detectable fast, and slow.
• The slow phase followed first-order kinetics with a rate constant of approximately 3 x 10(-3) s(-1) for Bence Jones proteins.
• Refolding of the VL domain appeared faster than the CL domain, and CL domain refolding kinetics mirrored that of isolated CL fragments.
• Activation energies for the slow phase were identical for Bence Jones proteins and their CL fragments.

Conclusions:

• The refolding kinetics of the CL domain are similar to those of the isolated CL fragment.
• VL domain refolding precedes CL domain refolding, despite similar immunoglobulin folds.
• The overall refolding of Bence Jones proteins cannot be simply described as the sum of isolated VL and CL fragment refolding kinetics.