Table 3. Modified C-terminal peptides identified from CPG70 tryptic digests using the Orbitrap MS with and without the inclusion of 0.2 M glycine in the growth medium.
CPG70 was purified from W50ABK*WbaP.
| Mass Obs (Da) | a Delta Mass (Da) | b Best Match | b Error (ppm) | c Relative Intensity | c Relative Intensity (Gly) |
|---|---|---|---|---|---|
| 1421.6930 | 0 (ref) | Water | 0 (ref) | 100 | 100 |
| 1705.8414 | 284.1484 | G(VQ) | 0 | 90 | 58 |
| 1664.8160 | 243.1230 | G(VS) | 4 | 78 | 64 |
| 1707.8204 | 286.1274 | GTQ | 0 | 30 | 11 |
| 1816.9090 | 395.2160 | GLPQ | 1 | 28 | 18 |
| 1688.8514 | 267.1584 | GLP | 0 | 27 | 17 |
| 1799.8934 | 378.2005 | LQH | 2 | 23 | 17 |
| 1708.8414 | 287.1484 | S(VT) | 1 | 20 | 13 |
| 1923.9314 | 502.2384 | (GMWK) | 4 | 20 | - |
| 1846.9210 | 425.2280 | SLPQ | 1 | 18 | 12 |
| 1549.7858 | 128.0929 | K | 13 | 17 | - |
| 1722.8574 | 301.1644 | SLT | 2 | 17 | 9 |
| 1577.7934 | 156.1004 | R | 3 | 15 | - |
| 1420.7088 | -0.9842 | Ammonia | 2 | 13 | 12 |
| 1478.7134 | 57.0210 | G | 4 | - | 219 |
a The delta mass is the observed mass minus the observed mass of the unmodified (water-cleaved) peptide (KAEDYIEVILDD, 1421.6930 Da). With the exception of the glycine-modified peptide, all observed masses are taken from the untreated sample.
b The best match is the metabolite most closely matching the accurate delta mass value using the Metlin database (see Methods). In every case, the best match was a peptide or amino acid. For peptides, the order of amino acids was inferred from the MS/MS data, with the order of bracketed amino acids being uncertain. The mass error (in ppm) associated with this search is provided in the next column.
c The intensity of the strongest MS peak, relative to the unmodified reference peak for the untreated sample. The values for the glycine-treated sample are provided in the next column.