Extended Data Fig. 8. Mass spectrometric analysis of GP2 glycopeptides detects the oligomannose-5 structure attached to N65.

Supporting MS2 spectrum of precursor m/z 1170.46, ⁶¹DPCQNYTLL⁶⁹, carrying oligomannose-5 (HexNAc2Hex5). Prepared by Asp-N digestion of the GP2 branch purified from HEK293T cells. N-glycan structures are depicted following the Consortium for Functional Glycomics (CFG) notation: HexNAc, N-acetylglucosamine (blue square); Hex, mannose (green circle). The cysteine residue is carbamidomethylated. Detected peptide-backbone fragment ions are presented in the peptide sequence. Interestingly, complex-type carbohydrate structures were also found to be attached to N65. This is consistent with the observation that, although UMOD N275 and GP2 N65 are both located in the groove between the β-hairpin and the D10C domain of the respective decoy modules, N65 is relatively more exposed than N275 in the structure (Extended Data Fig. 7a), making the N65 glycan chains more susceptible to modification.