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Decreased thermodynamic stability as a crucial factor for familial amyloidotic polyneuropathy
Tara Nath Niraula1, Katsuki Haraoka, Yukio Ando
1Graduate School of Science and Technology, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan.
Abstract:
A single mutation in the wild-type transthyretin (WT TTR) such as V30M causes a familial amyloidotic polyneuropathy disease. Comparison of the three-dimensional crystal structures of WT and V30M does not tell much about the reason. High-pressure NMR revealed that at neutral pH both WT and V30M exist as equilibrium between the native tetramer and the dissociated/unfolded monomer. The native tetramer is highly stable in WT (deltaG(0)=104 kJ/mol at 37 degrees C, pH 7.1), but the stability is significantly reduced in V30M (deltadeltaG(0)=-18 kJ/mol), increasing the fraction of the unfolded monomer by a 1000-fold. Significant reduction of thermodynamic stability of WT TTR by mutation could be a crucial factor for familial amyloidotic polyneuropathy.
Insights
Familial amyloidotic polyneuropathy arises from mutations in transthyretin (TTR). Reduced TTR protein stability due to mutations significantly increases unfolded monomers, a key factor in disease development.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biophysics
Background:
- Familial amyloidotic polyneuropathy (FAP) is linked to mutations in wild-type transthyretin (WT TTR).
- Structural comparisons of WT TTR and V30M mutant TTR do not fully explain disease mechanisms.
- Understanding the thermodynamic stability of TTR is crucial for FAP pathogenesis.
Purpose of the Study:
- To investigate the impact of the V30M mutation on transthyretin's thermodynamic stability.
- To elucidate the relationship between TTR stability, monomer dissociation, and FAP disease.
Main Methods:
- High-pressure Nuclear Magnetic Resonance (NMR) spectroscopy at neutral pH.
- Thermodynamic analysis of protein stability (deltaG(0)) and stability changes (deltadeltaG(0)).
Main Results:
- Both WT TTR and V30M TTR exist in equilibrium between native tetramers and dissociated/unfolded monomers at neutral pH.
- The native tetramer of WT TTR is highly stable (deltaG(0)=104 kJ/mol at 37°C, pH 7.1).
- The V30M mutation significantly reduces TTR stability (deltadeltaG(0)=-18 kJ/mol), increasing unfolded monomer fraction by 1000-fold.
Conclusions:
- The V30M mutation drastically decreases the thermodynamic stability of transthyretin.
- Reduced TTR stability and increased unfolded monomer levels are critical factors in the development of familial amyloidotic polyneuropathy.