Mass spectrometric contributions to the practice of phosphorylation site mapping through 2003: a literature review.

Reversible phosphorylation of proteins is among the most important post-translational modifications, and elucidation of sites of phosphorylation is essential to understanding the regulation of key cellular processes such as signal transduction. Unfortunately phosphorylation site mapping is as technically challenging as it is important. Limitations in the traditional method of Edman degradation of (32)P-labeled phosphoproteins have spurred the development of mass spectrometric methods for phosphopeptide identification and sequencing. To assess the practical contributions of the various technologies we conducted a literature search of publications using mass spectrometry to discover previously unknown phosphorylation sites. 1281 such phosphorylation sites were reported in 203 publications between 1992 and 2003. This review examines and catalogs those methods, identifies the trends that have emerged in the past decade, and presents representative examples from among these methods.