neoNtermini

Neo-N-termini are newly formed protein N-termini that arise when a protease cleaves a polypeptide, creating a novel starting amino group at the cleavage site. These termini are distinct from the native N-terminus encoded by the gene and may carry post-translational modifications such as acetylation. Neo-N-termini thus mark proteolytic processing events rather than initial translation starts.

Proteolytic processing that yields neo-N-termini occurs in various biological contexts, including protein maturation and activation, regulated degradation, and signaling events. It is also common during apoptosis, immune responses, and pathogen interactions, where specific proteases generate characteristic neo-N-termini on substrate proteins. Studying these termini helps map protease activity and substrate repertoires across conditions and organisms.

Detection of neo-N-termini relies on N-terminomics, a set of mass spectrometry–based approaches designed to identify newly generated N-termini. Methods such as TAILS (Terminal Amine Isotopic Labeling of Substrates), COFRADIC, and PICS enrich for neo-N-termini by blocking intact N-termini and selectively capturing newly formed ones, followed by MS analysis to locate cleavage sites and infer the responsible proteases.

Significance lies in identifying protease substrates, delineating proteolytic pathways, and understanding regulatory mechanisms in health and disease. Neo-N-terminomics informs protein annotation by revealing processing events and supports research into cancer, neurodegeneration, and immune signaling. Limitations include experimental bias, incomplete proteome coverage, and the challenge of distinguishing in vivo cleavage from artifacts of sample handling or in vitro processing.