PMID: PMC4739677-2-6

 

    Legend: Gene, Sites

Title : Identification of the O-glycan Com position

Abstract :
  1. For an automated glycopeptide spectra filtering and glycan fragment annotation the use of commercial software tools was considered, but turned out to be too error-prone in our case (data not shown)
  2. Hence, in the present work we relied on manual annotation and interpretation of low-energy CID- MS2 fragment spectra in order to elucidate the O-glycan com position-however, at the expense of throughput and the possibility to report false discovery rates
  3. In total we were able to characterize 88 O-glycopeptides with respect to their O-glycan com position
  4. The detected O-glycan com positions most likely correspond to mucin-type core-1 mono- and disialylated O-glycans ((di)sialyl-T-antigen)
  5. In agreement with literature, glycopeptides carrying disialylated O-glycans, were found in later eluting HILIC fractions (#15–#17), as the additional sialic acid renders the molecule more hydrophilic
  6. Mono- and disialylated glycoforms could be usually discriminated by the presence of distinct oxonium ions: whereas fragmentation of monosialylated O-glycans generated a characteristic oxonium ion at m/z 454.16 (Hex1NeuAc1) , disialylated O-glycans gave rise to an additional intense peak at m/z 495.18 (HexNAc1NeuAc1) (supplemental Fig
  7. S6, 266EAVPPVVDPDAPPSPPL283, m/z 818.683+, 267AVPPVVDPDAPPSPPL283, m/z 872.733+)
  8. Furthermore, in disialylated species characteristic fragment ions of the peptide\+HexNAc\+NeuAc ere observed
  9. In a few cases the glycan annotation was compromised by the presence of fragment ions corresponding to hexose rearrangement products (68, 69)
  10. Generally, it is important to note, that low-energy CID- MS2 fragmentation of glycopeptides does usually not produce fragment ions that relate to the linkage of the attached monosaccharides
  11. Therefore, validation of the inferred O-glycan structures using dedicated O-glycomics approaches, including for instance (reductive) beta-elimination or hydrazinolysis, is recommended
  12. However, our findings are in good agreement with literature, as mono- and disialylated mucin-type core-1 O-glycans are known to be present on the majority of secreted blood plasma glycoproteins , produced by hepatic cells of healthy individuals (79)
  13. Notably, a study on plasma-derived von Willebrand factor could show, that apart from mucin-type core 1 O-glycans (T-antigen), more complex O-glycan structures including ABH blood group antigen containing mucin-type core-2 ([GalNAcβ1–6-(Galβ1–3)-GalNAcα-O-Ser/Thr]) , can be present on human blood plasma glycoproteins , too (80)
  14. In the present work, analyzing the total human blood plasma O-glycoproteome, we could not detect any (glyco) peptide derived from von Willebrand factor , nor could we find any indication for the presence of fucosylated ( ABH blood group antigens) and/or LacNAc extended mucin-type core-2 O-glycans
Output (sent_index, trigger, protein, sugar, site):
  • 1. glycopeptide, , -, -, glycopeptide
  • 10. glycopeptides, , -, -, glycopeptides
  • 12. glycoproteins, , glycoproteins, -, -
  • 13. glycoproteins, , glycoproteins, -, -
  • 3. O-glycopeptides, , -, -, O-glycopeptides
  • 5. glycopeptides, , -, -, glycopeptides
Output(Part-Of) (sent_index, protein, site):
*Output_Site_Fusion* (sent_index, protein, sugar, site):

 

 

Protein NCBI ID SENTENCE INDEX