Table I. LTQ-FT MS analysis of O-glycosylated apoE peptides isolated from macrophages.
The 34-kDa band of apoE was excised after 1-DE (see legend to Fig 3) and subjected to LTQ-FT MS/MS. Separate analyses were undertaken for cell lysate apoE and apoE secreted into media. Peptide sequence AATVGSLAGQPLQER corresponds to apoE(192–206), and peptide sequence VQAAVGTSAAPVPSDNH corresponds to apoE(283–299). XICs are included in supplemental Fig. 1.
| Glycan | Peptide AATVGSLAGQPLQER (mass, 1496.7947) |
Peptide VQAAVGTSAAPVPSDNH (mass, 1619.7903) |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cellular apoE |
Secreted apoE |
Cellular apoE |
Secreted apoE |
|||||||||
| Observed mass (0 charge) | Theoretic mass | Mass difference | Observed mass (0 charge) | Theoretic mass | Mass difference | Observed mass (0 charge) | Theoretic mass | Mass difference | Observed mass (0 charge) | Theoretic mass | Mass difference | |
| ppm | ppm | ppm | ppm | |||||||||
| None | 1496.79 | 1496.79 | −1.710 | 1496.79 | 1496.79 | −0.895 | 1619.79 | 1619.79 | −1.222 | 1619.79 | 1619.79 | −0.926 |
| HexNAc | 1699.88 | 1699.87 | 1.182 | 1822.87 | 1822.87 | 2.299 | 1822.88 | 1822.87 | 3.286 | |||
| Hex-HexNAc | 1861.93 | 1861.93 | −0.091 | 1861.93 | 1861.93 | 0.038 | 1984.93 | 1984.93 | −0.408 | 1984.92 | 1984.93 | −1.728 |
| Hex-HexNAc-NeuAc | 2153.03 | 2153.03 | −0.980 | 2153.02 | 2153.03 | −1.770 | 2276.02 | 2276.02 | −0.822 | 2276.02 | 2276.02 | 0.053 |
| Hex-HexNAc-(NeuAc)2 | 2444.12 | 2444.12 | 0.745 | 2444.12 | 2444.12 | −0.777 | 2567.11 | 2567.12 | −1.843 | 2567.12 | 2567.12 | −1.375 |
| Hex2-(HexNAc)2 | 2227.07 | 2227.07 | −1.976 | 2227.06 | 2227.07 | −2.483 | ||||||
| Hex2-(HexNAc)2-NeuAc | 2518.17 | 2518.17 | −0.036 | 2518.17 | 2518.17 | 1.346 | ||||||
| Hex2-(HexNAc)2-(NeuAc)2 | 2809.26 | 2809.26 | −1.289 | 2809.26 | 2809.26 | −0.295 | ||||||