Table 1

Occupancy of key phosphorylation sites

Gwl site in Xenopus, Gwl site in DrosophilaRatio of peak area (%) for Gwl site with indicated treatment ina:
Xenopus, DrosophilaXenopus only
WT−OAWT+OAWT−OA +CDKbKD−OA +CDKKD+OA
pT193, pS220—, 658, 67211411
pT206, pT227c—, 0.228, 24NFNFNF
pS212, pS233c—, 0.29, 24
pT748, pT7060.2, 0.32, 117211
pS883, pS840—, 1742, 7651
  • a Values are percentages calculated as the ratios of the peak areas for all phosphorylated species/all species (phosphorylated plus unphosphorylated) of the peptide with the indicated residue. Xenopus and Drosophila Gwl sites in the same row correspond to each other. All peptides were generated by trypsin digestion except for the peptide including pT206 (Xenopus; chymotrypsin) and that including pS883 (Xenopus; endoproteinase Glu-C). The MS-analyzed samples analyzed here are shown in Fig. 2C. WT−OA and KD−OA indicate WT and KD, respectively, Xenopus Gwl grown in the absence of OA that was either untreated or treated in vitro with Cdk2/cyclin A (+CDK); WT+OA and KD+OA indicate active WT and KD, respectively, frog or fly Gwl grown in the presence of OA. Dashes indicate that phosphorylated forms of the peptide were not detected; NF (not found) indicates that neither phosphorylated nor unphosphorylated forms of the peptide were detected.

  • b Xenopus Gwl grown without OA (−OA) was activated by Cdk2/cyclin A to approximately 10% of the specific activity of Gwl grown with OA (+OA).

  • c Values for pT227 and pS233 in fly Gwl were determined from a single peptide containing a mixture of the two monophosphorylated forms.