Glycobiology Advance Access published online on February 24, 2009
Glycobiology, doi:10.1093/glycob/cwp025
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Structural analysis of N-glycans from gull egg white glycoproteins and egg yolk IgG
2 Department of Biology, The Johns Hopkins University, Baltimore, MD, 21218, USA
3 Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Chiba, 277-8562, Japan
4 Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan
5 NRPGM Core Facilities for Proteomics and Glycomics, Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, 115, Taiwan
1 To whom correspondence should be addressed. Noriko Suzuki, Tel: +81-4-7136-3617, Fax: +81-4-7136-3619, Email: nrsuzuki{at}k.u-tokyo.ac.jp Yuan C. Lee, Tel: +1-410-516-7041, Fax: +1-410-516-8716, Email: yclee{at}jhu.edu
Received on January 7, 2009; accepted on February 16, 2009
We previously showed that expression of (Gal
1–4Gal)-bearing glycoproteins among birds is related to their phylogeny. However, precise structures of (Gal1–4Gal)-containing N-glycans were only known for pigeon egg white glycoproteins and IgG. To compare structural features of (Gal1–4Gal)-containing N-glycans from other species, we analyzed N-glycans of gull egg white (GEW)-glycoproteins, ovomucoid, and ovotransferrin, and gull egg yolk IgG by HPLC, mass spectrometry (MS) and MS/MS analyses. GEW-glycoproteins included neutral, monosialyl and disialyl N-glycans, and some of them contained Gal1–4Gal sequences. Bi-, tri-, and tetra-antennary oligosaccharides that lacked bisecting GlcNAc were the major core structures, and incomplete -galactosylation and sialylation as well as the presence of diLacNAc on the branches generated microheterogeneity of the N-glycan structures. Moreover, unlike pigeon egg white glycoproteins, the major sialylation in GEW-glycoproteins is 2,3-, but not 2,6-, linked sialic acids (NeuAc). In addition to the complex-type oligosaccharide, hybrid-type oligosaccharides that lack bisecting GlcNAc were also abundant in GEW-glycoproteins. Gull egg yolk IgG also contained Gal1–4Galβ1–4GlcNAcβ1- sequences, but unlike pigeon IgG, no Gal1–4Galβ1–4Galβ1–4GlcNAcβ1- sequence was detected. Bi- and tri-antennary complex-type oligosaccharides with bisecting GlcNAc and with core fucosylation as well as high mannose-type oligosaccharides were the major structures in gull IgG. Our data indicated that some N-glycans from both GEW-glycoproteins and gull IgG contain the Gal1–4Galβ1–4GlcNAcβ1- sequence, but the ratio of -Gal-capped residues to non--Gal-capped residues in the non-reducing termini of N-glycans is much lower than in those of pigeon glycoproteins.
Key words:
egg yolk IgG
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Gal1–4Galβ1–4GlcNAc
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galabiose
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glycan diversity
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MS analysis
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