Table 1.
Identification of phosphorylation sites on mouse brain SV2A
| Peptides identified by mass spectrometry | Mass | Mascot score | Possible P sites | % Probability (PD1.4 pRS3.1) |
|---|---|---|---|---|
| >150 kDa | ||||
| R.GGLSDGEGPPGGR.G + P (ST) | 1234.4310 | 64 | S127 | 100 |
| R.GGLSDGEGPPGGRGEAQR.R + P (ST) | 1775.6966 | 35 | S127 | 100 |
| R.GEGAQDEEEGGASSDATEGHDEDDEIYEGEYQGIPR.A + 2 P (ST) | 4000.3955 | 66 | S80, 81 | 98, 98 |
| R.GEGAQDEEEGGASSDATEGHDEDDEIYEGEYQGIPR.A + 3 P (ST) | 4080.3606 | 32 | S80, S81, T84 | 100, 100, 100 |
| 75–150 kDa | ||||
| R.VFSVTHIK.T + P (ST) | 1009.4332 | 44 | S393 | 99 |
| R.GGLSDGEGPPGGR.G + P (ST) | 1234.4322 | 72 | S127 | 100 |
| R.GGLSDGEGPPGGRGEAQR.R + P (ST) | 1775.6939 | 50 | S127 | 100 |
| R.GEGAQDEEEGGASSDATEGHDEDDEIYEGEYQGIPR.A + P (ST) | 3920.4297 | 90 | S81 | 88 |
| R.GEGAQDEEEGGASSDATEGHDEDDEIYEGEYQGIPR.A + 2 P (ST) | 4000.3966 | 60 | S81 and either of S80 or T84 | 53, 92, 53 |
| R.GEGAQDEEEGGASSDATEGHDEDDEIYEGEYQGIPR.A + 3 P (ST) | 4080.3698 | 66 | S80, S81, T84 | 100, 100, 100 |
Endogenous SV2A was immunoprecipitated from mouse brain extract (8 mg). The immunoprecipitates were electrophoresed on a polyacrylamide gel, and after Colloidal blue staining, bands corresponding to SV2A were excised and digested with trypsin. Phosphorylated peptides were identified by LC-MS/MS analysis. The data analysis was as in Materials and Methods. The sequence of each peptide is shown with possible phosphorylation sites underlined. Also shown are the mass of the peptide, the Mascot score [of the peptide identification, in which individual ion scores >21 indicate identity or extensive homology (p < 0.05)], and the percentage probability of the phosphosite assignment, as determined by the phosphoRS 3.1 component of the Proteome Discoverer 1.4 software.