Nterminomics

Nterminomics is a field within proteomics dedicated to the comprehensive analysis of protein N-termini. It focuses on identifying and quantifying natural N-terminal peptides, proteolytically generated neo-termini, and N-terminal post-translational modifications such as acetylation. By profiling the repertoire of protein starts and processing events, Nterminomics helps define proteoforms and maturation pathways that are not captured by conventional proteomics. The work relies on mass spectrometry and specialized sample preparation to enrich and detect N-terminal peptides against a background of internal peptides.

Core methods in Nterminomics employ strategies that selectively capture or distinguish N-terminal regions. Two widely used approaches are COFRADIC (combined fractional diagonal chromatography) and TAILS (Terminal Amine Isotopic Labeling of Substrates). COFRADIC manipulates peptide chemistry and chromatography to separate N-terminal from internal peptides, facilitating identification of the starting points of proteins and their processing products. TAILS uses blocking of internal amino groups and subsequent removal of internal peptides to enrich N-terminal sequences for analysis. Other protocols rely on differential isotopic labeling or affinity capture to enable quantitative and qualitative assessment of N-termini, including those that are acetylated or otherwise modified.

Applications of Nterminomics include mapping protease substrates and cleavage events, characterizing maturation and trafficking of secreted or membrane proteins, and exploring alternative translation initiation and proteoform diversity. The approach is used to study developmental processes, disease-related proteolysis, and biomarker discovery, among other areas.

Challenges include the low abundance of many N-terminal peptides, distinguishing in vivo termini from artefacts of sample handling, and accurately interpreting neo-termini in the context of proteolysis. Advances in instrumentation and bioinformatics continue to enhance sensitivity, specificity, and the ability to integrate N-terminomics data with broader proteomics efforts.