Identification of Protein Phosphorylation Sites by Advanced LC-ESI-MS/MS Methods

Abstract

Phosphorylation, the process by which a phosphate group is attached to a preexisting protein, is an evolutionarily and metabolically cheap way to change the protein’s surface and properties. It is presumably for that reason that it is the most widespread protein modification: An estimated 10–30% of all proteins are subject to phosphorylation. MS-based methods are the methods of choice for the identification of phosphorylation sites; however biochemical pre-fractionation and enrichment protocols will be needed to produce suitable samples in the case of low-stoichiometry phosphorylation. Using emerging MS-based technology, the elucidation of the “phosphoproteome,” a comprehensive inventory of phosphorylation sites, will become a realistic goal. However, validating these findings in a cellular context and defining their biological meaning remains a daunting task, which will inevitably require extensive and time-consuming additional biological research.