Table 1.
Tryptic Fragments of the 70 kDa-Immunoreactive Protein Identified by LC/ESI/MS/MS as Originating from iPLA2β Proteina
| ID | obs mlz | z | Mr (calc) | Mr (exp) | delta | MC | iPLA2β peptide sequence |
|---|---|---|---|---|---|---|---|
| 10 | 955.03 | +2 | 1908.06 | 1908.01 | 0.05 | 0 | 7-LVNTLSSVTNLFSNPFR-23 |
| 6 | 663.82 | +2 | 1325.62 | 1325.61 | 0.01 | 0 | 26-EVSLADYASSER-37 |
| 9 | 614.01 | +3 | 1839.02 | 1839.00 | 0.02 | 1 | 38-VREEGQLILLQNQSNR-53 |
| 7 | 503.25 | +3 | 1506.72 | 1506.72 | 0.00 | 0 | 347-GEHGNTPLHLAM*SK-360 |
| 5 | 601.82 | +2 | 1201.63 | 1201.61 | 0.02 | 0 | 396-QLQDLMPVSR-405 |
| 4 | 583.33 | +2 | 1164.64 | 1164.63 | 0.01 | 0 | 408-KPAFILSSM*R-417 |
| 1 | 470.74 | +2 | 939.46 | 939.45 | 0.01 | 1 | 490-M*KDEVFR-496 |
| 8 | 570.30 | +3 | 1707.87 | 1707.85 | 0.02 | 0 | 497-GSRPYESGPLEEFLK-511 |
| 3 | 555.81 | +2 | 1109.61 | 1109.60 | 0.01 | 0 | 538-QPAE†LHLFR-546 |
| 2 | 517.75 | +2 | 1033.49 | 1033.48 | 0.01 | 0 | 547-NYDAPEAVR-555 |
Tryptic digest prepared from the iPLA2β-immunoreactive protein in the 70 kDa protein region was analyzed by LC/ESI/MS/MS, and peptide sequences were obtained following tandem analyses.
Data were processed by Mascot and MassLynx Softwares, and the peptides listed were found to be identical to tryptic fragments expected from the iPLA2β protein. ID, fragment number assigned based on mass identification by MALDI/TOF/MS (Figure 4); obs mlz, observed mass with charge state of z; Mr, calculated and expected mass of peptide; delta, mass difference between the calculated and expected values; MC, number of cleavage sites missed by trypsin during the in-gel digestion procedure; and the last column lists the peptide sequences that matched amino acid residues in the iPLA2β protein. (M*, oxidized methionine; E†, pyroglutamate; and RE and KD, missed trypsin cleavage sites).