Nitrosylated UCHL1 promoted surface assisted nucleation of α-synuclein and accelerated its fibrillation. (a) Time-course quantification of amyloid fibril formation by Thioflavin-T (ThT) binding assay. UCHL1 (200 μM) with 10 molar excess of GSNO accelerated fibrillation of α-synuclein by decreasing the lag phase. TM in nitrosative stress condition behaved like UCHL1 wild type and showed no effect on lag phase, confirming that only nitrosylated UCHL1 promotes α-synuclein fibrillation. (b) Samples at 0 h, 8 h, 16 h, and 24 h at 37 °C were aliquoted and processed for atomic force microscopy. The nitrosylated UCHL1 showed fibrils at 8 h but monomeric or oligomeric structures were observed in other samples at same time point.