Fig. 2: The sequence of P1 (³⁶GVLYVGS⁴²) is crucial for amyloid formation.

Fibrillation of WT αSyn at pH 7.5 or 4.5 measured by a ThT fluorescence and b, c, negative stain TEM, showing the end points of the experiment at b pH 4.5 (20 mM sodium acetate) and c pH 7.5 (20 mM Tris-HCl) (each in 200 mM NaCl). d–f, as for a–c, but for ΔP1. g–i, as for a–c, but for P1-SG-αSyn. Each condition was measured in at least triplicate. Note that short, clumped fibrils result at pH 4.5, presumably as fibril formation is rapid and the pH is close to the pI of the proteins. The results show that the sidechains of P1 are essential for rapid fibril formation at both pH values. A schematic of the sequence of αSyn is shown above each ThT plot, with the N-terminal region in blue, NAC in pink and the C-terminal region in red. The presence or absence of the P1 region is highlighted in each case. % pellet and t₅₀ values for these experiments are shown in Supplementary Table 1a. Source data are provided as a Source Data file.