Direct measurement of site-specific phosphorylation stoichiometry can unambiguously distinguish whether the degree of phosphorylation is regulated by upstream kinase/phosphatase activity or by transcriptional regulation to alter protein expression level. Here, we describe a motif-targeting quantitative proteomic approach that integrates dephosphorylation, isotope tag labeling, and enzymatic kinase reaction for large-scale phosphorylation stoichiometry measurement of the human proteome.
Keywords: Dimethyl labeling; Immobilized metal ion affinity chromatography (IMAC); Kinase reaction; Mass spectrometry; Motif-targeting; Phosphorylation stoichiometry; Proteomics.