The Folding Pathway of 6aJL2

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Light chain amyloidosis (AL) is linked to the λ6 germ line family, despite its low expression in healthy individuals.
• The inherent properties of λ6 proteins are suspected to contribute to AL pathogenesis.
• A recombinant model, 6aJL2, was previously studied, suggesting a simple two-state folding model, though some data hinted at an intermediate.

Purpose of the Study:

• To elucidate the detailed folding mechanism of the λ6 protein model 6aJL2.
• To identify kinetically accessible and equilibrium-populated species during protein folding.
• To compare the folding pathway of 6aJL2 with other light chain proteins.

Main Methods:

• Classic equilibrium and kinetic experiments were employed.
• Analysis of protein folding pathways was conducted.
• Size exclusion chromatography, fluorescence, and circular dichroism were utilized.

Main Results:

• A five-species folding mechanism for 6aJL2 at 25°C was proposed, involving intermediate and native-like species.
• The formation of intermediates in 6aJL2 folding was observed to be rapid.
• This folding mechanism is consistent with other proteins sharing a similar fold.

Conclusions:

• The folding of 6aJL2 is more complex than previously thought, involving multiple species and intermediates.
• The rapid formation of intermediates in 6aJL2 may contribute to its higher amyloidogenic potential compared to other light chains.
• Understanding this detailed folding mechanism is crucial for insights into light chain amyloidosis.