Probing the Dissociation Pathway of a Kinetically Labile Transthyretin Mutant

Area of Science:

• Biochemistry
• Structural Biology
• Biophysics

Background:

• Transthyretin (TTR) aggregation causes amyloid diseases.
• TTR amyloidosis involves dissociation of native tetramers into monomers.
• Dissociation at neutral pH is poorly understood due to low intermediate populations.

Purpose of the Study:

• To characterize TTR dissociation and reassembly at neutral pH.
• To determine the populations of species formed during A25T variant dissociation.
• To investigate the structural basis of TTR destabilization.

Main Methods:

• 19F-nuclear magnetic resonance (NMR) with trifluoromethyl probes.
• Analysis of concentration- and temperature-dependent species populations.
• Thermodynamic and kinetic parameter extraction using van't Hoff and NMR line shape analysis.
• All-atom molecular dynamics simulations.

Main Results:

• A tetramer-dimer-monomer (TDM) equilibrium model was proposed for A25T variant.
• Thermodynamic and kinetic parameters for tetramer dissociation were determined.
• Interfacial perturbations were identified as a common feature in destabilized TTR species.
• Molecular dynamics revealed increased F87 side chain dynamics in the A25T dimer.

Conclusions:

• Quantitative insights into the TTR dissociation energy landscape at neutral pH were obtained.
• The study elucidates the mechanism of TTR destabilization and aggregation.
• This work provides a foundation for understanding and potentially treating TTR amyloidosis.