Title: comprehensive terminomic characterization of biological systems.
Protein termini carry valuable information related to protein activity, localization, interaction and stability. Learning these various properties can be detrimental to the complete understanding of different biological systems. Characterization of all protein termini (terminome) by standard proteomic approaches is challenging due to their small amounts in the whole proteome sample. Therefore, enrichment methods for the N- and C-termini of proteins have been developed, and they have provided insights that would otherwise be difficult to obtain. Yet, all current enrichment methods have many limitations preventing them from revealing the complete terminome. Aiming to in-depth characterization of protein termini and their modifications, we developed two methods that we termed LATE and CAPE as novel N-terminal and C-terminal enrichment methods. We deployed our methods in various biological systems. Among our key findings was the cross-talk between proteolysis and post-translational Nt-acetylation, which we identified and characterized in apoptosis. In addition, we discovered hundreds of novel putative substrates of caspase-3 and highlighted a putative proteolysis-derived translation inhibition mechanism.