Table 1. Peptide fingerprint analysis of C-terminal SMN cleavage product.
| Peptide Source | SMN Peptide Identified | Tryptic/Non-tryptic | Peptide m/z | MASCOT Ion Score |
| Untreated | None | NA | NA | NA |
| 1U Calpain1 | S192*FLPPPPPMoxPGPR*L205 | Non-tryptic | 1318.7067 | 9 |
| F193*LPPPPPMPGPR*L205 | Non-tryptic | 1155.6343 | 56 | |
| F193*LPPPPPMoxPGPR*L205 | Non-tryptic | 1171.6345 | 24 | |
| R204*LGPGKPGLK*F214 | Tryptic | 866.5449 | 40 | |
| 2U Calpain1 | S192*FLPPPPPMPGPR*L205 | Non-tryptic | 1302.7100 | 71 |
| S192*FLPPPPPMoxPGPR*L205 | Non-tryptic | 1318.7010 | 27 | |
| F193*LPPPPPMPGPR*L205 | Non-tryptic | 1155.6340 | 65 | |
| F193*LPPPPPMoxPGPR*L205 | Non-tryptic | 1171.6300 | 47 | |
| R204*LGPGKPGLK*F214 | Tryptic | 866.5366 | 52 |
HIS6-SMN/GST-Gemin2 heterodimers were either untreated or cleaved with 1 or 2U of Calpain1. Bands containing the C-terminal calpain cleavage products were excised and subjected to peptide fingerprint analysis. An equivalent area in the untreated control sample was also analyzed. Nine peptides were identified (italics), four of which were in oxidized form (ox). Asterisks indicate the proteolytic cleavage sites. Non-tryptic peptides reveal the Calpain cleavage sites. Peptide m/z and MASCOT ion scores for each peptide are reported.