Table 2.

Suggested sequences for the phosphopeptides on the tryptic peptide maps

Peptide number on Fig. 3 Peptide number on Fig. 4 and Table 1 Manual Edman degradation: % label released on cycle number Total number of cycles Suggested sequence
1 6 3 (60%), 6 (30%), D (< 10%) 6 TYpSLGpSAL
2 3 3 (70%), 4 (20%), D (<10%) 6 LRpSpSMPGVR
3 3 3 (50%), 4 (30%), D (<10%) 6 LRpSpSMPGVR
4 7 6 (30%), D (>60%) 14 ETNLEpSLPLVDTHSK
5 1,2 1 (30%), 3 (30%), 5 (<10%), 6 (10%), D (<10%) 6 pSVpSSpSpSYR
6 1,2 5 (60%), 6 (30%), D (<10%) 6 SVSSpSpSYR
7 1,2 6 (70%), D (<10%) 6 SVSSSpSYR
8 5 6 (90%), D (<10%) 6 SLYSSpSPGGAYVTR
9 4 No release, D(>90%) 6 DGQVINEpTpSQHHDDLE
  • Manual Edman degradation was carried out on the phosphopeptides eluted from the TLC plates used for peptide mapping; D, disc. The results indicate the cycle when release of the label was observed. The suggested sequence for the peptide is partly based on the available sequence information and partly based on the knowledge of migration characteristics of previously isolated known phosphopeptides. The phosphorylation sites of peptide 4 to Thr-457 and Ser-458 were assigned based on Chou et al. (Chou et al., 1996).