In-gel N-acetylation for the quantification of the degree of protein in vivo N-terminal acetylation

Maturation of protein N-termini occurs in all kingdoms of life, with major protein modifications being proteolytic processing (e.g., removal of initiator methionines) and N-terminal acetylation. The functional consequences of these modifications are only known for a few substrates, and techniques to study such modifications have begun to emerge only recently. We here report on a method enabling targeted, mass spectrometry based analysis of protein N-termini from polyacrylamide gel-separated proteins. In our method, stable isotope incorporation by in-gel N-acetylation of free primary amines permits calculating the extent of in vivo N-terminal acetylation, proven to reveal crucial information with reference to N-terminal protein biology