Protein amino-terminal modifications and proteomic approaches for N-terminal profiling

•N-terminal acetylation, pyroglutamate formation, N-degrons and proteolysis are reviewed.•N-terminomics provide comprehensive profiling of modification at protein N-termini in a proteome-wide manner.•We outline a number of established methodologies for the enrichment of protein N-termini through positive and negative selection strategies.•Peptidomics-based approach is beneficial for the study of post-translational processing of protein N-termini. Amino-/N-terminal processing is a crucial post-translational modification affecting almost all proteins. In addition to altering the chemical properties of the N-terminus, these modifications affect protein activation, conversion, and degradation, which subsequently lead to diversified biological functions. The study of N-terminal modifications is of increasing interest; especially since modifications such as proteolytic truncation or pyroglutamate formation have been linked to disease processes. During the past decade, mass spectrometry has played an important role in facilitating the investigation of N-terminal modifications. Continuous progress is being made in the development and application of robust methods for the dedicated analysis of native and modified protein N-termini in a proteome-wide manner. Here we highlight recent progress in our understanding of protein N-terminal biology as well as outlining present enrichment strategies for mass spectrometry-based studies of protein N-termini.