Fig. 6: NAI/NAIA-5 couple allows identification of oxidized cysteines in cells under oxidative stress by MS experiment.

a Schematic cartoon illustrating the working principle of NAI/NAIA-5 couple in MS to identify oxidized cysteines, which show a larger LFQ ratio when comparing H2O2-treated cells with control. Created using ChemDraw, BioRender.com, and MS Powerpoint. b Number of NAIA-5-modified peptides detected in the MS experiments. Quantified data were the average values from n = 2 different replicates/groups. c Analysis of the LFQ intensity of NAIA-5 labeled peptides in H2O2-stimulated cells vs control revealed 583 highly oxidized cysteines in cells pretreated with H2O2, while 112 cysteines showed low NAIA-5 labeling in the H2O2-stimulated cells. d GO analysis on the percentage of the identified cysteines in response to hydrogen peroxide and oxidative stress. e Heatmap showing LFQ intensities (normalized by the intensity of the control group) of important classes of cysteines in response to oxidative stress. f Comparison of cysteines with significant changes in reactivity identified by our NAI/NAIA-5 with the results from reported Cysteine-reactive Phosphate Tag (CPT). We have successfully identified 338 unique cysteines, including those that are important for cellular responses to hydrogen peroxide and oxidative stress and can undergo disulfide oxidation.