Figure 3.

A) Sequence alignment of model eukaryotic PLK4 activation segments, omitting the ‘DFG’ motif, and ending at the ‘APE’ motif. Conserved Ser/Thr amino acids are outlined in blue, and con-served Y170^PLK4 is outlined in red. B) Coomassie blue staining of 3 μg of PLK4 proteins separated by SDS-PAGE. C) Collision dissociation product ion tandem mass spectra identifying phosphorylation of T177^PLK4 or D) dual phosphorylation of T170^PLK4 and Y177^PLK4 in the same PLK4 phosphoshopeptide. Matched product ions are indicated.