Fig. 4.

Acetylation of both ORF and neo N-terminal peptides.A, the ORF N-terminal peptides identified in HCT116 cells overexpressing caspase-3 and their control were categorized based on the presence of initiation methionine (marked as first Met) or its removal (marked as second position) and the presence of Nt-acetylation (“Nt-Acet”; in shades of blue) or its absence (“Free”; in shades of pink). B, the abundance ratio distribution of the ORF N-terminal peptides in cells overexpressing caspase-3 and their control, based on their N-terminal state (free/acetylated) and the presence of Asp or Glu residue in their sequence. Box limits indicate the 25th and 75th percentiles; whiskers extend 1.5 times the interquartile range from the 25th and 75th percentiles; crosses represent sample means; data points are plotted as open circles. n = 128, 808, 133, 620 sample points. C, the abundance ratio distribution of the 122 ORF N-terminal peptides that were identified both as Nt-acetylated and with free N terminus and contain Asp or Glu in their sequence. Center lines show the medians; box limits indicate the 25th and 75th percentiles; whiskers extend 1.5 times the interquartile range from the 25th and 75th percentiles; data points are plotted as open circles. D, posttranslational neo-Nt-acetylation sites that were identified at N termini generated following known proteolytic processing of precursor proteins as indicated in UniProt. The blue diamonds represent identification in biological repeats or time points. HYTANE, hydrophobic tagging-assisted N-termini enrichment; LATE, LysN amino terminal enrichment.