Fig. 4.

Quantitative subtiligase-TM N terminomics in pervanadate-treated vs. untreated cells. (A) Pervanadate treatment leads to proteolytic shedding of cell surface proteins. (B) Western blot showing an accumulation of phosphotyrosine on pervanadate treatment of cells. (C) Volcano plot showing the log₂-fold change of N termini measured by quantitative mass spectrometry in pervanadate-treated vs. untreated cells. The significance of the changes is indicated by the −log₁₀ P value (y-axis). (D) Flow cytometry validation of changes in the N-terminal proteome observed in the mass spectrometry dataset. Monoclonal antibodies that bind epitopes N-terminal to the observed cleavage site were chosen such that a decrease in signal on pervanadate treatment was expected.