Figure 1. The ERK‐dependent phosphoproteome in ES cells.

1. Experimental workflow.
2. Volcano blot illustrating fold changes and statistical significance of identified phosphopeptides from the S1 fraction. Red circles represent log2 fold changes with P‐adj < 0.05. Results are from identifications in three independent experiments.
3. MS1 and MS2 mass spectra of RSK1 phosphopeptide. Left panel: The monophosphorylated peptide exhibits an approximate fivefold increase when ERK is active. Right panel: Fragmentation mass spectrum. Phosphorylation at Ser352 could be deduced from a mass increment of 167 Da between ions b₄ and b₅.
4. Immunoblots of pRSK1 (Ser352) and total RSK1 in ES cells in the indicated conditions.

Source data are available online for this figure.