Identification of protein phosphorylation sites by advanced LC-ESI-MS/MS methods

Phosphorylation, the process by which a phosphate group is attached to a pre-existing 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 wide-spread 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 prefractionation 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.