Each of the modified peptides identified from cortactin is listed, with the phosphorylated residue(s) shown in red. Phosphorylation sites in brackets could not be specified unambiguously. In most experiments, the cells were treated with phosphatase inhibitors before lysis. Relative peptide abundance is expressed in terms of peak areas observed for all charge states of particular peptides. Peak areas for the most abundant phosphopeptides are displayed as ++++; those with areas that are decreased by a factor of 10, 100 and 1000 are shown as +++, ++ and +, respectively. Phosphopeptides that were not identified without inhibitor treatment are indicated as -. Peptides labeled `IMAC' were only observed after enrichment of the sample by immobilized metal-affinity chromatography.