1 Department of Chemistry and Bioscience, The Faculty of Engineering and Science, Aalborg University, VBN2 Department of Life Sciences and Chemistry, Roskilde University, 1 Universitetsvej, DK-4000 Roskilde
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 pKa values change dramatically in the fibrillar state.
F E B S Letters, 2010, Vol 584, Issue 4, p. 780-784