Table IV.
In vitro substrate trapping identified eight proteins that both bound to the active site of PTP1B and were hyperphosphorylated at Tyr(P) sites in PTP1B-deficient cells
wt, wild type, pY, phosphotyrosine; pS, phosphoserine; pT, phosphothreonine; (0.5), 50% phosphorylation probability.
| Name | Qualitative Tyr(P) peptide analysisa
|
nsb (nc) | Up-regulated inc
|
Quantitative substrate trappingd protein ratio trap/wt | Already described (reference) | |||
|---|---|---|---|---|---|---|---|---|
| Tyr(P) site | Phosphopeptide sequence | Basal | EGF | PDGF | ||||
| p120ctn | 280 | FHPEPpYGLEDDQR | 9 (5) | X | 7.29 | |||
| 257 | QDVpYGPQPQVR | X | ||||||
| LPP | 245 | SAQPSPHYMAGPSSGQIpYGPGPR | 5 (3) | X | ||||
| 301/302 | YYEPpYpYAAGPSYGGR | X | ||||||
| 318 | SEGDTApYGQQVQPNTWK | X | ||||||
| Cortactin | 421 | KQpTPPApSPSPQPIEDRPPpS(0.5) pS(0.5)PIpYEDAAPFK | 2 (2) | X | 2.62 | (42) | ||
| 334 | NASTFEEVVQVPSApYQK | X | ||||||
| ZO-1 | 1164 | TSTLRHEEQPAPApYEVHNR | 1 (1) | X | 2.80 | |||
| Rho GTPase-activating protein 12 | 3 (0) | X | 21.08 | |||||
| PLCγ1 | 771 | IGTAEPDpYGALYEGR | 4 (4) | X | X | 43.96 | ||
| SHIP2 | 1136 | TLSEVDpYAPGPGR | 1 (1) | X | ||||
| p120RasGAP | 451 | EIpYNTIR | 1 (1) | X | 47.62 | |||
| p62DOK | 295 | TVPPPVPQDPLGpSPPALpYAEPLDSLR | 6 (4) | (X) | 12.66 | (40) | ||
| 376 | GLpYDLPQEPR | (X) | ||||||
| 450 | GFSSDTALpYSQVQK | (X) | ||||||
| Epidermal growth factor receptor | 1197 | GPTAENAEpYLR | 5 (5) | 7.69 | (49) | |||
| 1172 | GSHQMSLDNPDpYQQDFFPK | |||||||
| 1000 | MHLPSPTDSNFpYR | |||||||
| 1069/1092 | pYSSDPTGAVTEDNIDDAFLPVPEpYVNQSVPK | |||||||
| Platelet-derived growth factor receptor β | 751 | DESIDpYVPMLDMK | 4 (3) | 17.89 | (49) | |||
| 763/778 | pYADIESPSYMAPYDNpYVPSAPER | |||||||
Tyr(P) peptides are shown that belong to proteins that bound to PTP1B substrate-trapping mutants.
The number ns indicates how many Tyr(P) peptides were identified in the substrate-trapping experiment, and nc indicates how many of these Tyr(P) peptides were also identified under physiological cellular conditions.
Proteins found with significantly up-regulated Tyr(P) peptides (p value < 0.1) are indicated by X. Tyr(P) peptides from the described PTP1B substrate p62DOK are indicated by (X), as they were not found with p values of less than 0.1.
PTP1B substrate-trapping mutant/wild-type enzyme ratios are listed.