Fig. 2.

The statistics of identified phosphopeptides. A, Column diagram showing the number of phosphopeptides according to the number of unambiguously identified phosphorylation sites in a single peptide. If a phosphorylation site was identified in more than one peptide, it was counted repeatedly every time on every peptide. B, Number of phosphorylation sites according to the phosphorylated amino acid (serine, threonine, or tyrosine) identified. If a phosphorylation site was identified in more than one peptide, it was counted only once.