FIGURE 2.

GalNAc-T2 glycosylated Thr²²⁶ of the ANGPTL3 peptide. Characterization of the product formed by GalNAc-T2 with the ANGPTL3 peptide by ETD in the LTQ-Orbitrap. A, MS¹ of ANGPTL3 + 1Tn; B, ETD-MS² of precursor MH₄⁴⁺ ion (200 ms activation time); C, ETD-MS² of precursor MH₃³⁺ ion (150 ms activation time). Inset, fragmentation scheme for ANGPTL3 + 1Tn, illustrating the numbering of product ions generated by c/z^• cleavage. The fragmentation pattern is consistent with glycosylation of Thr⁸ with a HexNAc residue (*) (i.e. abundant z·₅⁺, z·₆⁺, c₇⁺, c₉⁺, and related ions (c_n ± 1 mass unit and/or doubly charged) were detected at m/z values calculated for HexNAc at T8. Corresponding fragments consistent with glycosylation at T7 were not detected. All detected fragment ions are listed in supplemental Table 1.