Table 3. Characterization by MALDI–TOF MS and ESI-MS/MS of N-terminal PIP2 peptides from a root PM extract.
Measured mass (Da) [M+H]+ | Predicted peptide sequence | Determined peptide sequence | Modification | Isoform | Position in the sequence |
---|---|---|---|---|---|
886.46 | KWSFYR | None | PIP2;1/PIP2;6 | 34–39/33–38 | |
1234.56 | DVEGPEGFQTR | None | PIP2;2 | 4–14 | |
1340.65 | DLDVNESGPPAAR | None | PIP2;4 | 4–16 | |
1404.70 | DVEAVPGEGFQTR | DVEAVPGEGFQTR | None | PIP2;1 | 4–16 |
1418.70 | DVEAVPGEGFQTR+14 Da | 1me | PIP2;1 | 4–16 | |
1433.70 | AKDVEGPEGFQTR | Tag PEGFQTR | M1 cleaved | PIP2;2 | 2–14 |
1447.70 | AKDVEGPEGFQTR+14 Da | M1 cleaved+1me | PIP2;2 | 2–14 | |
1461.70 | AKDVEGPEGFQTR+28 Da | M1 cleaved+2me | PIP2;2 | 2–14 | |
1475.70* | AKDVEGPEGFQTR+42 Da | AKDVEGPEGFQTR | M1 cleaved+2meK3+1me | PIP2;2 | 2–14 |
1539.78 | AKDLDVNESGPPAAR | M1 cleaved | PIP2;4 | 2–16 | |
1603.80 | AKDVEAVPGEGFQTR | AKDVEGPEGFQTR | M1 cleaved | PIP2;1 | 2–16 |
1617.80 | AKDVEAVPGEGFQTR+14 Da | M1 cleaved+1me | PIP2;1 | 2–16 | |
1631.80† | AKDVEAVPGEGFQTR+28 Da | AKDVEAVPGEGFQTR | M1 cleaved+2meK3 | PIP2;1 | 2–16 |
1645.80† | AKDVEAVPGEGFQTR+42 Da | AKDVEAVPGEGFQTR | M1 cleaved+2meK3+1meE6 | PIP2;1 | 2–16 |
1869.93 | DYVDPPPAPLLDMGELK | None | PIP2;7 | 16–32 | |
1872.90 | DYQDPPPAPFIDGAELK | DYQDPPPAPFI/LDGAELK | None | PIP2;1 | 17–33 |
2000.99 | DYQDPPPAPFIDGAELKK | DYQDPPPAPFI/LDGAEL/IKK | None | PIP2;1 | 17–34 |
2066.96 | DYKDPPPAPFFDMEELR | None | PIP2;4 | 17–33 | |
2096.94 | DYEDPPPTPFFDADELTK | DYEDPPPTPFFDADEL/ITK | None | PIP2;2 | 15–32 |
*The peptide sequence was deduced from PSD fragmentation. Lys3 was shown to be dimethylated (2meK3). The additional 14 Da mass increment indicates the presence of a methyl group that must be positioned within the following sequence DVEGPEGFQTR.
†Peptide, the ESI-MS/MS spectrum of which is shown in Figure 2.