Fig. 2.

Phosphopeptide abundance distributions. (A and B) Log₂-transformed light:heavy (arrested:asynchronous) ratios for all quantified phosphopeptides from G₁ (A) and M (B) phase arrested cells. Bins are 0.5 units wide; e.g., the ‘0′ bin stretches from −0.25 to +0.25. (Insets) Shown is the distribution of unphosphorylated peptides in each experiment. (C) Peptides with ≥2.5-fold changes were deemed regulated and those with ≤1.5-fold changes unregulated. (D and E) Log₂ phosphopeptide abundance distributions for peptides with different phosphorylation motifs are shown for G₁ phase cells (D) and for mitotic cells (E). Phosphorylation sites were classified into 1 of 3 motifs, [pS/pT]-P, [pS/pT]-X-X-[D/E], or [K/R]-X-X-[pS/pT]. Sites lacking these motifs were grouped into “other.” Only peptides containing a single motif class were included in the analysis.