2P-35 PDF
Identification and quantification of phosphorylation: a synthetic peptide treated with a Ser/Thr-kinase
Usual phosphorylation of a protein proceeds enzymatically to add phosphate group(s) to the hydroxy group(s) at Ser/Thr/Tyr residues. In case of multiple sites of phosphorylation being found in a protein, it is required not only to identify the sites of phosphorylation, but also to quantify the degree of phosphorylation at each site. We report here a typical example of the analysis of multiple phosphorylation sites by using a synthetic peptide treated with a Ser/Thr-kinase derived from Arabidopsis thaliana. Following identification of the phosphorylation sites of the reaction product by MS/MS, it was subjected to LC-MS for relative quantification of phosphorylation at each site. We will also present the usefulness of an in-house software “Isomatch-Web” for identification of phosphorylation sites.