The role of protonation in protein fibrillation

Many proteins fibrillate at low pH despite a high population of charged side chains. Therefore exchange of protons between the fibrillating peptide and its surroundings may play an important role in fibrillation. Here, we use isothermal titration calorimetry to measure exchange of protons between buffer and the peptide hormone glucagon during fibrillation. Glucagon absorbs or releases protons to an extent which allows it to attain a net charge of zero in the fibrillar state, both at acidic and basic pH. Similar results are obtained for lysozyme. This suggests that side chain pK a values change dramatically in the fibrillar state.

[1]  H. Fukada,et al.  Enthalpy and heat capacity changes for the proton dissociation of various buffer components in 0.1 M potassium chloride , 1998, Proteins.

[2]  D. Otzen,et al.  Glucagon amyloid-like fibril morphology is selected via morphology-dependent growth inhibition. , 2007, Biochemistry.

[3]  Jesper Søndergaard Pedersen,et al.  The changing face of glucagon fibrillation: structural polymorphism and conformational imprinting. , 2006, Journal of molecular biology.

[4]  Kenjiro Ono,et al.  Kinetic modeling and determination of reaction constants of Alzheimer's beta-amyloid fibril extension and dissociation using surface plasmon resonance. , 2002, Biochemistry.

[5]  R. de Vries,et al.  Thermally induced fibrillar aggregation of hen egg white lysozyme. , 2005, Biophysical journal.

[6]  J. Frank,et al.  Time‐dependent insulin oligomer reaction pathway prior to fibril formation: Cooling and seeding , 2009, Proteins.

[7]  K. P. Murphy,et al.  Evaluation of linked protonation effects in protein binding reactions using isothermal titration calorimetry. , 1996, Biophysical journal.

[8]  Yuji Goto,et al.  Direct Measurement of the Thermodynamic Parameters of Amyloid Formation by Isothermal Titration Calorimetry* , 2004, Journal of Biological Chemistry.

[9]  D. Otzen,et al.  N- and C-terminal hydrophobic patches are involved in fibrillation of glucagon. , 2006, Biochemistry.

[10]  Jianing Zhang,et al.  Simulations of nucleation and elongation of amyloid fibrils. , 2009, The Journal of chemical physics.

[11]  D. Otzen,et al.  Sulfates dramatically stabilize a salt-dependent type of glucagon fibrils. , 2006, Biophysical journal.

[12]  Jean-Christophe Rochet,et al.  Novel therapeutic strategies for the treatment of protein-misfolding diseases , 2007, Expert Reviews in Molecular Medicine.

[13]  D. Otzen,et al.  Unique identification of supramolecular structures in amyloid fibrils by solid-state NMR spectroscopy. , 2009, Angewandte Chemie.