Title : General Remarks on Immunoglobulin O-glycoproteomics
Abstract :
- Another O-glycosylated protein that could not be identified in our study is Ig α-1 ( IgA1 )
- IgA1 is a high abundant human blood plasma glycoprotein that features a cluster of three to five mucin-type O-glycans in the hinge region of the heavy chain (81)
- This cluster harbors many prolines , hence corresponding Proteinase K generated peptides might have been not unambiguously identified (the tryptic IgA1 hinge region O-glycopeptide looks as follows: (K)89HYTNPSQDVTVPCPVPTPPTPPTPPTPPCCHPR126)
- Furthermore, because of the densely clustered O-glycans a potential IgA1 O-glycopeptide carrying mucin-type O-glycans at each potential site , such as PTPPTPPTPPTPPCC, might be too hydrophilic and consequently might have been among the (glyco) peptides present in the late eluting HILIC wash fraction
- Worth mentioning, in our study we could detect the IgA1 peptide 95QDVTVPCPVP105 in its nonglycosylated form (HILIC Fraction #11, CID, supplemental Table S2)
- Therefore, the O-glycosylation site S105 seems to be only partially occupied
- Surprisingly, human IgA1 O-glycopeptides have not been identified in any other large-scale glycoproteomic studies (30, 58, 60, 76, 77, 82)
- However, there is a targeted glycoproteomic study from Takahashi et al. focusing on IgA1 O-glycosylation (81)
- In this study the authors analyzed human plasma derived IgA1 O-glycopeptides (tryptic and nontryptic) with ESI-FT-ICR-MS/MS as well as ESI-LTQ-FT-MS/MS, both in online- and offline-Mode
- To pinpoint the O-glycosylation sites the authors have employed activated ion-electron capture dissociation (AI- ECD ) and ETD
- Another immunoglobulin that is reported to carry mucin-type O-glycans in the hinge region is Ig delta ( IgD ) (83)
- The plasma concentration of IgD is much lower than the concentration of IgA , IgG , and IgM but higher than that of IgE ( IgD represents 0.25% of total plasma immunoglobulins)
- Apart from the study conducted by Takayasu et al. from 1982 (83) on truncated O-glycopeptides (peptide\+GalNAc) at present no O-glycoproteomic data do exist for intact human IgD O-glycopeptides
- Also of particular interest is a recent finding by Plomp et al.: using a targeted glycoproteomics approach these authors could demonstrate, for the first time, that IgG3 is partially O-glycosylated in its hinge region (mucin-type core-1 O-glycans) (84)
Output (sent_index, trigger,
protein,
sugar,
site):
- 1. O-glycosylated, , protein, -, -
- 10. O-glycosylation, , -, -, sites
- 13. O-glycopeptides, , -, -, O-glycopeptides
- 14. O-glycosylated, , IgG3, -, region
- 2. glycoprotein, , IgA1, -, -
- 2. glycoprotein, , glycoprotein, -, -
- 3. O-glycopeptide, , -, -, region O-glycopeptide
- 4. O-glycopeptide, , -, -, O-glycopeptide
- 6. O-glycosylation, , -, -, site
- 7. O-glycopeptides, , -, -, O-glycopeptides
- 9. O-glycopeptides, , -, -, O-glycopeptides
Output(Part-Of) (sent_index,
protein,
site):
- 13. IgD, O-glycopeptides
- 3. IgA1, region O-glycopeptide
- 3. Proteinase K, peptides
- 4. IgA1, O-glycopeptide
- 7. IgA1, O-glycopeptides
- 9. IgA1, O-glycopeptides
*Output_Site_Fusion* (sent_index,
protein,
sugar,
site):