Table 2. Identification of Hpn and Hpn-2 proteins in samples prepared from different Helicobacter species by top-down proteomics.
| Strain | Protein | Calculated mass, Da 1 | Measured mass, Da 2 | Mass diff., ppm | Max number of matching fragments 3 | E- value 4 |
|---|---|---|---|---|---|---|
| Helicobacter pylori B8 | Hpn | 6937.6567 | 6937.6584 | 0.3 | 50 | 2.26E-108 |
| Hpn-2 | 7922.4546 | 7922.4806 | 3.3 | 40 | 9.17E-71 | |
| Helicobacter acinonychis (Str. Sheeba) | Hpn | 6969.7094 | 6969.7231 | 2.0 | 47 | 8.04E-104 |
| Hpn-2 | 7992.4496 | 7992.4586 | 1.1 | 12 | 6.75E-25 | |
| Helicobacter bizzozeronii (CGUG35545) | Hpn | 6608.5422 | 6608.5614 | 2.9 | 38 | 2.03E-75 |
| Helicobacter felis (ATCC 49179) | Hpn | 6491.6014 | 6491.5812 | -3.1 | 33 | 2.04E-65 |
| Helicobacter mustelae (12198) | Hpn | 7903.2685 5 | 7903.3145 | 5.8 | 40 | 6.97E-72 |
| 7772.2280 | 7772.2518 | 3.1 | 52 | 7.12E-91 | ||
| 7511.1166 6 | 7511.1444 | 3.7 | 50 | 1.39E-81 | ||
| 7424.0846 7 | 7424.1151 | 4.1 | 24 | 1.51E-42 | ||
| 7208.9940 8 | 7208.9918 | -0.3 | 51 | 9.56E-100 |
1 –Calculated monoisotopic mass, cysteine residues oxidized to cystines.
2 –Experimental monoisotopic mass.
3 –At 5 ppm matching tolerance.
4 –Expectation value, calculated by ProSightPC software. The expectation value (e value) is the number of sequences in a database that are expected to have P-scores equal to or better than what was observed simply by chance. A P-score is the probability of obtaining at least as good a match between the observed fragment list and a sequence as by chance. Low E-values represent better matches (less likely to be false positives) than high E-values.
5, 6, 7, 8 –forms of the protein with N-terminal Met retained (5) or N-terminal NF (6), NFS (7) or NFSTN (8) residues cleaved.