Title : Site-specific N-glycosylation of human
chorionic gonadotrophin--structural analysis of
glycopeptides by one- and two-dimensional 1H NMR spectroscopy
Abstract :
- Glycopeptides representing individual N-glycosylation sites of the heterodimeric glycoprotein hormone human chorionic gonadotrophin (hCG) were obtained from subunits hCG alpha (N-glycosylated at Asn-52 and Asn-78 ) and hCG beta (N-glycosylated at Asn-13 and Asn-30 ) by digestion with trypsin and chymotrypsin , respectively
- Following purification by reverse-phase HPLC and identification by amino acid sequencing, the glycopeptides were analysed by one- and two-dimensional 1H NMR spectroscopy
- The results are summarized as follows: (i) oligosaccharides attached to Asn-52 of hCG alpha comprised monosialylated 'monoantenary' NeuAc alpha 2-3Gal beta 1-4GlcNAc beta 1-2Man alpha 1-3[Man alpha 1-6]Man beta 1-4GlcNAc beta 1-4GlcNAc (N1-4'), disialylated diantennary NeuAc alpha 2-3Gal beta 1-4GlcNAc beta 1-2Man alpha 1-3[NeuAc alpha 2-3-Gal beta 1-4GlcNAc beta 1-2Man alpha 1-6]Man beta 1-4GlcNAc beta 1-4GlcNAc (N2), and the monosialylated hybrid-type structures NeuAc alpha 2-3Gal beta 1-4GlcNAc beta 1-2Man alpha 1-3[Man alpha 1-3Man alpha 1-6]Man beta 1-4GlcNAc beta 1-4GlcNAc (N1-A) and NeuAc alpha 2-3Gal-beta 1-4GlcNAc beta 1-2Man alpha 1-3[Man alpha 1-3(Man alpha 1-6)Man alpha 1-6]Man beta 1-4GlcNAc beta 1-4GlcNAc (N1-AB) in a ratio approaching 5:2: 2:1 ; (ii) Asn-78 of hCG alpha carried N2 and N1-4' almost exclusively (ratio approximately 3:2); (iii) both N-glycosylation sites of hCG beta contained predominantly component N2, partially (approximately 25%) and completely alpha 1-6-fucosylated at the N-acetylglucosamine linked to Asn-13 and Asn-30 , respectively
- The distinct site-specific distribution of the oligosaccharide structures among individual N-glycosylation sites of hCG appears to reflect primarily the influence of the surrounding protein structure on the substrate accessibility of the Golgi processing enzymes alpha-mannosidase II , GlcNAc transferase II and alpha 1,6-fucosyltransferase
Output (sent_index, trigger,
protein,
sugar,
site):
- 0. glycopeptides, , -, -, glycopeptides
- 1. N-glycosylated, , -, -, Asn-13 and Asn-30
- 1. N-glycosylated, , -, -, Asn-52 and Asn-78
- 1. N-glycosylated, , hCG beta, -, Asn-13 and Asn-30
- 1. N-glycosylated, , subunits hCG alpha, -, -
- 1. N-glycosylated, , subunits hCG alpha, -, Asn-13 and Asn-30
- 1. N-glycosylated, , subunits hCG alpha, -, Asn-52 and Asn-78
- 1. N-glycosylation, , glycoprotein hormone human chorionic gonadotrophin (hCG), -, -
- 1. N-glycosylation, , glycoprotein hormone human chorionic gonadotrophin (hCG), -, sites
- 1. glycoprotein, , glycoprotein hormone human chorionic gonadotrophin (hCG), -, -
- 2. glycopeptides, , -, -, glycopeptides
- 3. N-glycosylation, , hCG, -, sites
Output(Part-Of) (sent_index,
protein,
site):
- 1. glycoprotein hormone human chorionic gonadotrophin (hCG), sites
- 3. hCG, sites
*Output_Site_Fusion* (sent_index,
protein,
sugar,
site):
- 1. hCG beta, -, Asn-13 and Asn-30
- 1. subunits hCG alpha, -, Asn-13 and Asn-30
- 1. subunits hCG alpha, -, Asn-52 and Asn-78